1.1. What is LPRng?

The LPRng print spooler software was developed to be robust, reliable, secure, scalable, and portable. It has been used since 1988 in extremely demanding academic printing environments such as University of Minnesota, MIT, and Rutgers, commercial companies such as Dow Jones and Abbot Pharmaceuticals, as well as being distributed with Linux, FreeBSD, and other systems. Each of these environments has a unique set of problems, demanding various configuration and administrative capabilities. For example, the simple single user system with a single or limited number of printers requires easy configuration and simple diagnostic procedures, while the network based printing system requires highly robust error logging, authentication, and failover support. LPRng provides a highly flexible configuration system that allows it to perform optimally in all of these environments.

The LPRng software has three components: the lpd print spooler and the user client applications lpr, lpq, lprm, etc.; the IFHP print filter (ifhp) which is used to convert jobs into a suitable for a particular printer, and the the LPRngTool Graphic User Interface (lprngtool) which provides a simple and easy to use configuration and monitoring tool for the LPRng print spooler.

LPRng mimics many of the features of the vintage or legacy Berkeley (University of California - Berkeley) Line Printer (LPR) package found on Berkeley derivatives of the Unix operating system. LPRng will print a document with little or no knowledge of the content or special processing required to print the document on a stand-alone machine or in a distributed printing environment. New (as compared to Berkeley LPR) features include: lightweight lpr, lpc and lprm programs, dynamic redirection of print queues, automatic job holding, highly verbose diagnostics, load balancing queues; enhanced security (SUID not required in most environments), and easy configuration.

LPRng started life at the University of Waterloo in 1986 as PLP (Public Line Printer), a replacement for the original BSD lpd code. This was a one-shot effort by the author, Patrick Powell, to develop freely redistributed code without the restrictions of the BSD/AT&T license and would allow non-licensed sites to fix and patch problems. From 1988 to 1992 individuals and groups added features, hacked, slashed, and modified the PLP code, coordinated largely by Justin Mason (<jmason@iona.ie>) who started the LPRng mailing list.

In 1992 while at San Diego State University Prof. Powell redesigned and reimplemented the PLP code and named the result LPRng. The goals of the LPRng project were to build a server system that was as close to user abuse proof as possible, that would provide services limited only by the inherent capacities of the support system, RFC1179 compliant, and with extensive debugging capabilities to allow quick and easy diagnostics of problems.

In 1999 the code base for LPRng was again reorganized in order to provide a common method for running on non-UNIX platforms such as Microsoft Windows NT, Apple Rhapsody, and embedded systems.

As a side effect of this work, many security problems that could develop were identified and steps taken to ensure that they were not present in LPRng. For example, LPRng clients such as lpr, lprm, lpc, and lpq can run as ordinary users programs, the lpd server can run as a non-root user once a network port has been opened, and all text formatting operations done by LPRng use a very restricted and highly secure version of the snprintf function.

1.2. Additional Resources

The main LPRng documentation is the LPRng-HOWTO, which is available in several formats. Information about LPRng and the latest release can be found on the LPRng web page http://www.lprng.com/LPRng.html

The ifhp documentation is the IFHP-HOWTO, which is available in the ifhp distribution. Information about ifhp and the latest release can be found on the LPRng web page http://www.lprng.com/LPRng.html

There is also a mailing list at lprng@lprng.com. To post to the list you must subscribe by sending send an email to lprng-request@lprng.com, with the message subject or body containing the word `subscribe' or `help'.

Several presentations of LPRng and print spooling software have been made at the Large Installation System Administrator (LISA) conferences. The presentation at the LISA 98 conference is in the PowerPoint file LISA98.ppt in the LPRng distribution documentation.

1.3. Frequently Asked Questions

There are a list of Frequently Asked Questions that appear regularly on the LPRng mailing list. See The Most Frequently Asked Questions.

1.4. License, Copyright, and Disclaimer

The LPRng Print Spooler and the ifhp Print Filter software are distributed under the GNU Public License (GPL) and the Artistic License. Users can choose to redistribute or use the software under a license that is appropriate for their purpose. Other licenses and distribution agreements are available by contacting AStArt Technologies for information.

THE MATERIAL IN THESE SOFTWARE PACKAGES AND DOCUMENTS IS PROVIDED WITHOUT FEE AND AS-IS WITH NO WARRANTY REGARDING FITNESS OF USE FOR ANY PURPOSE. THE AUTHOR AND ALL CONTRIBUTORS ARE NOT LIABLE FOR ANY DAMAGES, DIRECT OR INDIRECT, RESULTING FROM THE USE OF THE SOFTWARE OR ANY INFORMATION PROVIDED IN THIS DOCUMENT.

1.5. Commercial Support

AStArt Technologies provides commercial support and enhancements for the LPRng and other network software. AStArt provides network and system consulting services for UNIX and NT systems, as well as real time and network software.

1.6. Web Site

Web Page: http://www.lprng.com

1.7. FTP Sites

Main FTP Site:

Mirrors:

1.8. Mailing List

To join the LPRng mailing list, please send mail to lprng-request@lprng.com with the word 'subscribe' in the BODY.

The LPRng mailing list is archived on http://www.findmail.com/list/lprng

1.9. PGP Public Key

The LPRng distributions have an MD5 checksum calculated, which is then signed with a PGP public key. Here is the key for validating the checksums:

    Type Bits/KeyID    Date       User ID
    pub  1024/00D95C9D 1997/01/31 Patrick A. Powell \
       <papowell@lprng.com>
    
    -----BEGIN PGP PUBLIC KEY BLOCK-----
    Version: 2.6.3i
    
    mQCNAzLygTQAAAEEANBW5fPYjN3wSAnP9xWOUc3CvsMUxjip0cN2sY5qrdoJyIhn
    qbAspBopR+tGQfyp5T7C21yfWRRnfXmoJ3FVtgToAsJUYmzoSFY08eDx+rmSqCLe
    rdJjX8aG8jVXpGipEo9U4QsUK+OKzx3/y/OaK4cizoWqKvy1l4lEzDsA2VydAAUT
    tCdQYXRyaWNrIEEuIFBvd2VsbCA8cGFwb3dlbGxAYXN0YXJ0LmNvbT6JAJUDBRA0
    XonoiUTMOwDZXJ0BAQ2cBAC7zU9Fn3sC3x0USJ+3vjhg/qA+Gjb5Fi1dJd4solc4
    vJvtf0UL/1/rGipbR+A0XHpHzJUMP9ZfJzKZjaK/d0ZBNlS3i+JnypypeQiAqo9t
    FV0OyUCwDfWybgAORuAa2V6UJnAhvj/7TpxMmCApolaIb4yFyKunHa8aBxN+17Ro
    rrQlUGF0cmljayBBLiBQb3dlbGwgPHBhcG93ZWxsQHNkc3UuZWR1PokAlQMFEDLy
    gTSJRMw7ANlcnQEBYBYD/0zTeoiDNnI+NjaIei6+6z6oakqO70qFVx0FG3aP3kRH
    WlDhdtFaAuaMRh+RItHfFfcHhw5K7jiJdgKiTgGfj5Vt3OdHYkeeh/sddqgf9YnS
    tpj0u5NfrotPTUw39n6YTgS5/aW0PQfO9dx7jVUcGeod1TGXTe9mIhDMwDJI4J14
    =3Zbp
    -----END PGP PUBLIC KEY BLOCK-----

1.10. References and Standards

The following references and standards have been used in the development of the LPRng software.

2.1. Getting Source Code and Support Programs

1. Obtain the latest or stable version of the LPRng source code from a LPRng FTP Site.

2. Obtain the latest or stable version of the ifhp filter source code from a LPRng FTP Site. This filter is used to support PostScript, PCL, and text printers.

3. Obtain the following GNU programs from one of the many GNU Software Mirror Sites and install them. See the directions in the GNU Zip distribution for details.

   GNU gzip Compression Utility

   Used to generate the compressed LPRng distribution.

   GNU tar Archive Utility

   GNU tar supports gzip compression and decompression and is used to generate the LPRng distribution.

   GNU make

   LPRng requires GNU make for configuration and installation.

   GNU gcc Compiler or ANSI C Compiler

   LPRng requires and ANSI C compiler. If you do not have an ANSI C compiler then please use the GNU gcc compiler.

   
   
   

4. Solaris Sparc and X86 Binaries for GCC and Make can be obtained from http://sunfreeware.com/.

5. While the following are not essential to LPRng they are used by the ifhp filter.

   file - File Identification Utility

   The Open Source file utility by Ian F. Darwin can be obtained from ftp://ftp.astron.com/pub/file/. This is a greatly improved version of the original UNIX file utility and may be used by the ifhp filter to do file recognition.

   gs - GhostScript

   GhostScript can be obtained from http://www.cs.wisc.edu/~ghost/ or http://www.ghostscript.com. GhostScript is a PostScript interpreter that allows you to translate PostScript to various printer compatible formats such as PCL, as well as displaying the code on a terminal. You might also want to get the PDF extensions that allows GhostScript to read and print PDF files.

   gv - GhostView

   Of course you will want to get the gv program that uses GhostScript to display PostScript on an X terminal. It can be obtained from http://wwwthep.physik.uni-mainz.de/~plass/gv/

   
   
   

2.2. PATH Environment Variable and Utilities

Make sure that directory where you you have installed the GNU tools is one of the first entries in the shell search PATH environment variable. For example, if you have installed the utilities in the (default) directory /usr/local/bin, this should be one of the first entries in the PATH. For example:

    PATH=/usr/local/bin:/bin:/sbin:/usr/bin

If you are compiling the distribution on a Solaris system you will need to use the utilities in the /usr/ccs/bin directory. This directory must be in the PATH after the directory where the GNU utilities have been installed. For example:

    PATH=/usr/local/bin:/bin:/sbin:/usr/bin:/usr/ccs/bin

Check to see that the GNU make utility and not the default OS make is being used by default. Use make -v to determine what version you are using:

2.3. Network Mounted File System and Spool Directories

The LPRng lpd print server makes heavy use of file locking to coordinate and synchronize process activities. Given the historical and ongoing problems of file locking on and NFS mounted file system, not to mention the high overhead for doing file locking in a distributed environment, it is strongly recommended that spool directories NOT be on an NFS mounted partition or on a partition that is NFS exported.

This warning extends to other network file systems as well.

In addition, the configuration file such as /etc/printcap must be available or printing will not function. Care should be taken to ensure that these files are stable and available at all times.

2.4. Daemon User and Daemon Group

The lpd server is started at system initialization time and initially runs as ROOT (Effective UID 0). It performs all file and other operations with non-privileged user daemon Effective UID and group daemon Effective GID, and does a setuid() to these UID and GID values when running programs. The client programs such as lpr operate with the effective user IDs of the user which started them.

Most UNIX systems already have user daemon and group daemon, or a similar ones. If suitable user and group IDs are not present then the appropriate system administration tools should be used to create them. The configuration --with-userid=UID and --with-groupid=GID can be used to specify the user and group IDs. The user ID must not have login capability.

2.5. Configuration

The LPRng package consists of the following executables and configuration files:

• lpd - the lpd print server program

• lpr, lpq, lprm, lpc, and lpstat client programs for printing, status queries, job removal, server configuration, and System V lpstat emulation respectively.

• printcap print queue database file which is used by all the server and client programs

• lpd.conf LPRng configuration options which is used by all the server and client programs

• lpd.perms permission information which is used by the lpd server to control user actions.

LPRng uses the configure script generated by the GNU autoconf utility to generate a set of Makefiles. These are used by GNU make to compile and install the LPRng software. The following Makefile variables and values are set by configure to specify the location of the LPRng software:

These are used to install the following files:

You can set explicit values for the paths by using the override --name=PATH. For example:

    ./configure --prefix=/usr --sysconfdir=/etc \
        --mandir=/usr/share/man

In addition to these standard configure options the following options provided.

It is recommended that you use one of the following configurations:

1. If you already have a print spooling system installed and want to install LPRng for testing purposes or as an alternative to the existing system and keep your existing print spooling system, use:

       ./configure
       
       use defaults for file locations and permissions:
         /usr/local/{bin,sbin,libexec/filters,man}
       requires lpd to run on the local host
       executables installed setuid ROOT
   

   
   
   

2. If you have manual pages in /usr/share/man, your existing print spooling system has executables in /usr/bin and /usr/sbin, and you want to replace your existing print spooling system, use:

       ./configure --prefix=/usr --sysconfdir=/etc \
         --mandir=/usr/share/man
       
       executables and files in
          /usr/{bin,sbin,libexec/filters}
          /usr/share/man/man[0-9]
       requires lpd to run on the local host
       everything installed setuid ROOT
   

   
   
   

3. If you have manual pages in /usr/share/man and allow jobs (by default) to be sent directly to the server host (lightweight operation), use:

       ./configure --prefix=/usr --sysconfdir=/etc \
          --mandir=/usr/share/man --disable-force_localhost
       
       executables and files in
          /usr/{bin,sbin,libexec/filters}
          /usr/share/man/man[0-9]
       does not require lpd to run on the local host
       everything installed setuid ROOT
   

   
   
   

2.6. System and User Printcap, lpd.conf, and lpd.perms files

The system printcap file contains the definitions of the print queues used by LPRng, and is located in the directory specified by the configuration ${sysconfdir} value. For a complete description of the printcap file see Printcap Database. If your system does not have an existing printcap file then a dummy file similar to the following is installed by default:

    # dummy printcap file
    lp:cm=Dummy Printcap Entry:
     :lp=/dev/null
     :sd=/var/spool/lpd/%P

In addition to the system printcap file, each user can have a ${HOME}/.printcap which contains printcap entries as well. The the user printcap file is in effect appended to the system printcap file, and values in the user printcap file override the system printcap file. However, in order to allow users to specify a default printer after reading the printcap file information the entries are sorted so that printcap entries defined by users come first.

The lpd.conf is located in the ${sysconfdir} directory and provides configuration settings for both the LPRng client and server programs. For a complete description of the lpd.conf file see Configuration File, Defaults and Overrides. During installation the ${sysconfdir}/lpd.conf.template is created with the default LPRng information and if there is not an existing ${sysconfdir}/lpd.conf file is copied to it.

The lpd.perms is located in the ${sysconfdir} directory and is only by lpd to determine user permissions for printing activities. For a complete description of the lpd.perms file see Permissions and Authentication for details. During installation the lpd.perms.template file is installed in the ${sysconfdir}/lpd.perms.template and if there is not an existing lpd.perms file is copied to it.

By default, the LPRng client programs lpr, lpq, lprm, and lprc will require a lpd.conf and printcap file to be installed on the local host. You can relax this requirement by setting using the --disable-require_configfile configuration option. You can also create empty files to satisfy the program requirements.

2.7. Checking System Installation with checkpc

The checkpc program is used to make sure that the spool directories and files used by LPRng have the correct permissions and are in place. By default, checkpc will check permissions and report if there are any problems. You should run this as root. For example:

    h4: {2} # checkpc
    Warning - No configuration file '/etc/lpd.conf'
    Warning - No lpd only printcap file found in '/etc/lpd_printcap'
    Warning -  ** cannot open '/var/run/lpd.printer' - 'Permission denied'
    Warning -  bad directory - /var/spool/lpd/lp
    Warning -   Printer 'lp' spool dir '/var/spool/lpd/lp' needs fixing

In the above example, checkpc has discovered that the lpd.conf file is missing. This is a serious problem and indicates that the software may be incorrectly installed.

The lpd only printcap message is usually of concern to administrators who wish to use some of LPRng's more exotic configuration options. It is possible to have separate printcap files for client and server programs. This is useful when printcap files get extremely large and cuts down substantially on system management problems.

The permission denied message for /var/run/lpd.printer is serious, as the lpd server uses this as a lock file.

The bad directory message about the spool directory is usually caused by wrong permissions or a missing directory.

The checkpc -f (fix) option causes checkpc to take action to rectify errors. The checkpc -f -V (verbose) option causes the fixup activity to be displayed a well:

    h4: {3} # checkpc -f -V
    Checking for configuration files '/etc/lpd.conf'
      found '/usr/local/etc/lpd.conf', mod 0100644
    Checking for printcap files '/etc/printcap'
      found '/usr/local/etc/printcap', mod 0100644
    Checking for lpd only printcap files '/etc/lpd_printcap'
     DaemonUID 1, DaemonGID 1
    Using Config file '/etc/lpd.conf'
    LPD lockfile '/var/run/lpd.printer'
     Checking directory: '/var/run'
       directory '/var'
       directory '/var/run'
      checking '/var/run/lpd.printer' file
    
    Checking printer 'lp'
     Checking directory: '/var/spool/lp'
       directory '/var'
       directory '/var/spool'
       directory '/var/spool/lp'
      file 'control.lp', zero length file unchanged in 1 hours
      file 'status.lp', zero length file unchanged in 1 hours
      file 'status', zero length file unchanged in 1 hours
      file 'log', zero length file unchanged in 1 hours
      file 'acct', zero length file unchanged in 1 hours
      checking 'control.lp' file
      checking 'status.lp' file
      checking 'status' file
      cleaning 'status' file, 0K bytes: no truncation
      checking 'log' file
      cleaning 'log' file, 0K bytes: no truncation
      checking 'acct' file
      cleaning 'acct' file, 0K bytes: no truncation

checkpc will create the spool directories and any missing files, and fix the permissions of existing files.

2.8. Compilation and Install

Once you have decided on the configuration you want and understand what files need to be installed, then you are ready to do the install. It is extremely simple to extract the files, configure, compile and install the software:

    h4: {4} % gunzip -c LPRng-<version>.tgz | tar xvf -
    h4: {5} % cd LPRng-<version>
    h4: {6} % ./configure  [ ... configuration options ]
    h4: {7} % make clean all
    h4: {8} % su   # you must do the following commands as root
    h4: {9} # make install
    h4: {10} # # if checkpc did not run, do the next command
    h4: {11} # # make sure checkpc and lpq are in your paths
    h4: {12} # # if using CSH, use 'rehash' as well
    h4: {13} # checkpc -f
    h4: {14} # # check to see if the server is running
    h4: {15} # lpq

During installation you may get an error message indicating that the lpd file could not be installed or the lpd server could not be started. If this is the case, then carry out the appropriate steps in Updating Print Spooler Software and Startup Scripts to remove the existing print spooling software and then try to reinstall LPRng. You should also to check the System Specific Notes section for any system specific installation requirements.

While the LPRng installation scripts try hard to set up the lpd server in place, you will still need to reboot your host and make sure that the various printing facilities are working correctly after reboot.

2.9. Installation Problems

Read the notes for your OS in section System-dependent notes for specific installation help (if any).

The following is a list of commonly encountered problems and their solution. If these do not solve your problem, then send mail to the lprng@lprng.com mailing list. You will have to subscribe to the list in order to post to the list.

1. Make complains about a malformed make or Makefile file, illegal syntax in the file, or illegal entries in the file. You are most likely not running GNU Make. You must use GNU make or you should be a Unix Wizard able to master the mysteries of converting GNU Makefiles to your local system make. It is easier to simply install GNU make.

2. The C Compiler complains about missing files or has a large number of errors. Use gcc instead of your vendor's C compiler.

       configure --with-cc=gcc
   

   
   
   

   If there are messages about missing system files, then you most likely have an incomplete set of system include files, or the include do not properly reference other required include files, or the include files are located in an unusual location. If you are using gcc then make sure that the gcc was carried out correctly on your system. The easiest way to assure this is to recompile and reinstall the gcc compiler.

3. If you have checked your compiler installation and are still missing libraries or files then the include files may be in /usr/local/include and libraries may be in /usr/local/include and these directories may not searched or used by the compiler by default. This can be fixed by using the --with-cppopts= and --with-ldopts= configure options.

       configure \
         --with-cppopts="-I/usr/local/include -I/usr/include/kerberosIV" \
         --with-ldopts="-L/usr/local/lib -L/usr/lib/kerberosIV"
   

   
   
   

4. The software compiles but will not run on the system. Make sure that you have followed your system specific rules for compiling and installing setuid ROOT programs on your system. You may need to statically link your executables.

5. The software was compiled on one system and copied to another system, but will not run on the other system. Try compiling the software on the target system. If it compiles and runs, then you most likely have an issue with libraries or Operating System Versions.

After you have installed the LPRng software and rebooted your system, do the following commands:

    h4: {16} # lpq
    Printer: lp@astart
     Queue: no printable jobs in queue

If you do not get status displayed, or you get some other error message, then the following are a series of tests can use to check that LPRng is installed correctly.

First we will run lpd in the foreground and are used to make sure that our system configuration is correct. You will need root permissions to do the following steps. Stop the running currently running lpd process. Next, run lpd in foreground mode:

    h4: {17} # ps -aux | grep lpd 
    daemon   240  0.0  0.0  1292    0  ??  IWs  -         0:00.00 lpd: lpd Waiting
    h4: {18} # kill 240
    h4: {19} # checkpc -f
    h4: {20} # /usr/local/bin/lpd -F -D1
    Fatal error - Another print spooler is using TCP printer port

If you get the above error message, then you have either not terminated the running lpd server, there is another process using TCP/IP port 515, or you are not starting the lpd server as ROOT. See the System Specific Notes for details on how to resolve these issues.

Correct the problem and then restart the server. You should see the output indicated below:

    h4: {21} # /usr/local/bin/lpd -F -D1
    1999-04-05-14:35:14.023 astart27 [2667] Waiting  lpd: LOOP START
    1999-04-05-14:35:14.024 astart27 [2667] Waiting  Get_max_servers: \
       getrlimit returns 256
    1999-04-05-14:35:14.024 astart27 [2667] Waiting  Get_max_servers: \
       returning 128
    1999-04-05-14:35:14.025 astart27 [2667] Waiting  lpd: \
       max_servers 128, active 0
    1999-04-05-14:35:14.025 astart27 [2667] Waiting  lpd: \
       starting select timeout 'yes', 600 sec

Now from another window do the following commands:

    h4: {22} # lpq
    Printer: lp@astart
     Queue: no printable jobs in queue

At this point your LPRng software has been installed and tested. See the Updating Print Spooler Software and Startup Scripts for details on how to automatically start lpd at boot time.

2.10. Updating Print Spooler Software and Startup Scripts

If you are replacing your existing print spooling spooling system, you must shut down and remove the existing print spooler software before installing the LPRng software. This process is fairly system dependent, and requires a small amount of system expertise.

To assist in this process the LPRng installation has a set of preinstall, postinstall, preremove, and postremove scripts in the distribution that may be suitable for your local system use. If these fail to work during the system installation, you will need to carry out the steps described here by hand.

    h4: {26} # ps -auxw |grep lpd
    papowell 23932  0.0  0.3  224  184  p3  S+  10:40AM  0:00.01 grep lpd
    daemon  17763  0.0  0.2  448  120  ??  IWs  29Mar99  0:01.35 (lpd)
    h4: {27} % kill 135
    h4: {28} % kill 135
    135: No such process

    h4: {29} # find /usr -type f -name lp\*  -print >/tmp/candidates
    h4: {30} # find /sbin -type f -name lp\*  -print >>/tmp/candidates
    h4: {31} # cat /tmp/candidates
    /usr/bin/lpunlock
    /usr/bin/lpqall.faces
    /usr/bin/lpq             <---- old
    /usr/bin/lpr             <---- old
    /usr/bin/lprm            <---- old
    /usr/bin/lptest
    /usr/doc/samba-1.9.18p10/examples/printer-accounting/lp-acct
    /usr/man/man1/lpq.1
    /usr/man/man1/lpr.1
    /usr/man/man1/lprm.1
    /usr/man/man1/lptest.1
    /usr/man/man4/lp.4
    /usr/man/man8/lpc.8
    /usr/man/man8/lpd.8
    /usr/sbin/lpc            <--- old
    /usr/sbin/lpd            <--- old
    /usr/sbin/lpf            <--- old
    h4: {32} # mv /usr/bin/lpq  /usr/bin/lpq.old
    h4: {33} # mv /usr/bin/lpr  /usr/bin/lpr.old
    h4: {34} # mv /usr/bin/lprm /usr/bin/lprm.old
    h4: {35} # mv /usr/sbin/lpc /usr/sbin/lpc.old
    h4: {36} # mv /usr/sbin/lpd /usr/sbin/lpd.old
    h4: {37} # mv /usr/sbin/lpf /usr/sbin/lpf.old

    h4: {38} # checkpc -f
    h4: {39} # lpd
    h4: {40} # lpq
    Printer: lw4@h2  'Hp : LaserWriter'
     Queue: no printable jobs in queue
     Status: job 'root@h2+884' removed at 11:27:25.864
     Filter_status: done at 11:27:25.766
    h4: {41} # lpr /etc/motd
    h4: {42} # lpq
    Printer: lw4@h2  'Hp : LaserWriter'
     Queue: no printable jobs in queue
     Status: job 'root@h2+888' removed at 11:27:25.864
     Filter_status: done at 11:33:17.020

    #!/bin/sh
    # This is an effort to automate the setup
    #  needed to install the LPRng software on the
    #  Solaris OS.  This is effectively a one way path.
    #  You are warned.
    PATH=/etc:/usr/etc:/usr/bin:/bin:/sbin:/usr/sbin:$PATH
    # remove the init.d entry and links
    for i in /etc/rc*.d/*lp ; do
        b=`basename $i`;
        d=`dirname $i`;
        mv $i $d/UNUSED.$b.UNUSED
    done
    # rename files
    renameit () {
        for i in $* ; do
            if [ -f $i -a '!' -f $i.old ] ; then
                echo "renaming $i $i.old";
                mv $i $i.old
            fi
        done
    }
    renameit /usr/bin/lp /usr/bin/lpstat /usr/sbin/lpadmin \
      /usr/sbin/lpfilter /usr/sbin/lpforms /usr/sbin/lpmove \
      /usr/sbin/lpshut /usr/sbin/lpsystem /usr/sbin/lpusers \
      /usr/ucb/lpc /usr/ucb/lpq /usr/ucb/lpr /usr/ucb/lprm \
      /usr/ucb/lptest /usr/lib/lp/lpsched /usr/lib/lp/lpNet
    # remove the cron entry
    if [ -f /var/spool/cron/crontabs/lp ] ; then
        mv /var/spool/cron/crontabs/lp \
           /var/spool/cron/UNUSED.crontabs.lp
    fi
    # comment out inetd.conf entry
    if egrep '^printer' /etc/inetd.conf >/dev/null 2>\& ; then
        mv /etc/inetd.conf /etc/inetd.conf.bak
        sed -e 's/^printer/# printer/' </etc/inetd.conf.bak \
           >/etc/inetd.conf
    fi
    # remove the nlsadmin entry
    nlsadmin -r lpd tcp
    nlsadmin -r lp tcp
    echo REBOOT SYSTEM and then install LPRng

    h4: {43} # cd /
    h4: {44} # find . -type f -exec grep -l lpsched {} \; -print >/tmp/files
    h4: {45} # cat /tmp/files
    /etc/rc0.d/K20lp
    /etc/rc2.d/K20lp
    /etc/rc2.d/S80lp
    /etc/init.d/lp
    h4: {46} # ls -l ` cat /tmp/files `
    lrwxrwxr-x 1 root bin 1 Dec 29 23:39 /etc/rc0.d/K20lp -> ../../init.d/lp
    lrwxrwxr-x 1 root bin 1 Dec 29 23:39 /etc/rc2.d/K20lp -> ../../init.d/lp
    lrwxrwxr-x 1 root bin 1 Dec 29 23:39 /etc/rc2.d/S80lp -> ../../init.d/lp
    -rwxr--r-- 5 root sys 460 Sep 1 1998 /etc/rcS.d/K39lp

    h4: {47} # find /usr -type f -name lp\* -print >/etc/printingfiles
    h4: {48} # cat /tmp/printingfiles
    /usr/bin/lp
    /usr/bin/lpstat
    /usr/lib/lp/bin/lp.cat
    /usr/lib/lp/bin/lp.set
    /usr/lib/lp/bin/lp.tell
    /usr/lib/lp/lpNet
    /usr/lib/lp/lpsched
    /usr/lib/lp/lpdata
    /usr/sbin/lpadmin
    /usr/sbin/lpfilter
    /usr/sbin/lpforms
    /usr/sbin/lpmove
    /usr/sbin/lpshut
    /usr/sbin/lpsystem
    /usr/sbin/lpusers
    /usr/ucb/lpc
    /usr/ucb/lpq
    /usr/ucb/lpr
    /usr/ucb/lprm
    /usr/ucb/lptest
    h4: {49} # vi /tmp/printingfiles  # remove ones you want to save
    h4: {50} # for i in ` cat /tmp/printingfiles ` ; do
    >  if [ -f $i -a '!' -f $i.old ] ; then  mv $i $i.old ; fi;
    > done

    printer stream tcp nowait root /usr/lib/print/in.lpd in.lpd

    h4: {51} # nlsadmin -v tcp
    lpd  \x00020203000000000000000000000000  ENABLED  \
      NORPC  root  NOMODULES  /var/spool/lp/fifos/listenBSD  #
    0  \x00020ACE000000000000000000000000  ENABLED    \
      NORPC  root  NOMODULES  /usr/lib/saf/nlps_server  #
    lp  NOADDR  ENABLED  NORPC  root  NOMODULES \
      /var/spool/lp/fifos/listenS5  #
    h4: {52} # nlsadmin -r lpd tcp
    h4: {53} # nlsadmin -r lp tcp

    h2.private: {2} # pmadm -l
    PMTAG    PMTYPE   SVCTAG   FLGS ID    <PMSPECIFIC>
    zsmon    ttymon   ttya     u    root  /dev/term/a I - /usr/bin/login ...
    zsmon    ttymon   ttyb     u    root  /dev/term/b I - /usr/bin/login ...

    h4: {54} # shutdown -y "Whooga! Whooga! Dive! Dive! System going down."

    h4: {55} # telnet localhost 515

    LPD_PATH=/usr/sbin/lpd
    SHOWALL=-e
    case "$1" in
      start)
            # Start daemons.
            /bin/echo "Starting lpd: \c"
            ${LPD_PATH}
            /bin/echo ""
            ;;
      stop)
            # Stop daemons.
            /bin/echo "Shutting down lpd: \c"
            kill -INT `ps ${SHOWALL} \
               | awk '/lpd/{ print $1;}'` >/dev/null 2>&1
            /bin/echo " server stopped";
            ;;
      *)
            echo "Usage: $0 {start|stop}"
            exit 1
            ;;
    esac

    h4: {56} # checkpc -f
    h4: {57} # /usr/sbin/lpd (or /usr/local/sbin/lpd)
    h4: {58} # lpq
    Printer: lp
     Queue: no printable jobs in queue

2.11. Emulation for UNIX SystemV lp and lpstat

Many utilities in the UNIX System V environment require the lp, lpstat, and cancel programs. It is almost impossible to modify these utilities, as many are vintage software which is unsupported or which would be too costly to update. In order to support these applications LPRng emulates the lp, lpstat, and clean programs. See the LPRng man pages for lp, lpstat, and cancel in the LPRng distribution for details and compatibility.

The LPRng lpstat emulator accepts the lpstat command line options returns status in a format that is close to the one that common lpstat implementations return. Unfortunately, due to the wide variety of different modifications and vendor versions of lpstat there are slight differences between the this status and the status returned by the original lpstat. If this is the case, then there is little to do but to modify the source code for lpstat and compile a version that implements the required format.

If the lpr program is invoked with the name lp, it will simulate the lp options. This can be done by making a symbolic link to the lpr program or by making a copy of the lpr program with the name lp.

    h4: {59} # cd /usr/bin
    h4: {60} # ln -s lpr lp
    h4: {61} # lp /tmp/hi
    request id is root@h4+489

Finally, if the lprm program is invoked with the name cancel it will simulate the cancel command. This can be done by making a symbolic link to the lprm program or by making a copy of the lprm program with the name cancel.

    h4: {62} # cd /usr/bin
    h4: {63} # ln -s lprm cancel
    h4: {64} # cancel 489
    cancel 513
    Printer lp@h9:
      checking perms 'root@h9+513'
      dequeued 'root@h9+513'

Many vintage or legacy applications have fully qualified paths to the lp and lpstat executables, and it may be necessary to make additional symbolic links or copies of the LPRng executables to satisfy their pathname requirements.

    h4: {65} # ln -s /usr/bin/lpr /usr/ucb/lpr

2.12. SAMBA and LPRng

The SMB network protocol is used by many Microsoft Operating Systems to implement file and printer sharing. SAMBA is a UNIX package that implements the SMB protocol and provides a simple and easy way to import and export file systems and printer facilities. The web site for SAMBA is http://www.samba.org. The SAMBA code is extremely easy to install and the SWAT (Samba Web Administration Tool) makes configuration almost trivial.

The See the SAMBA doc/text/Printing.txt and related documentation for details on printing. In the samba.conf file [global] section or in the SWAT page for printing configuration you need to specify the that you want to have Samba handle printing, the print, lpq, and lprm commands to be used when a user prints a job, asks for status, or removes a job, and a temporary directory to hold print jobs when they are submitted. The following is a simple example of to set up printing for authenticated users.

    [printers]
        path = /var/spool/lpd/samba
        #  ---  do not use the Samba default path = /tmp
        print ok = yes
        printing = lprng
        load printers = yes
        guest ok = no
        printcap name = /etc/printcap
        print command =      /usr/bin/lpr  -P%p -r %s
        lpq command   =      /usr/bin/lpq  -P%p
        lprm command  =      /usr/bin/lprm -P%p %j
        lppause command =    /usr/sbin/lpc hold %p %j
        lpresume command =   /usr/sbin/lpc release %p %j
        queuepause command = /usr/sbin/lpc  -P%p stop
        queueresume command = /usr/sbin/lpc -P%p start

1. Samba will make a copy of the files to be printed in the directory specified by path. If the print operation fails then sometimes the print file is left in the directory.

2. The directory should have the same ownership and permissions as /tmp, i.e.- owner and group root and bin, with 01777 permissions, where 01000 is the sticky bit.

   A directory whose `sticky bit' is set becomes an append-only directory, or, more accurately, a directory in which the deletion of files is re- stricted. A file in a sticky directory may only be removed or renamed by a user if the user has write permission for the directory and the user is the owner of the file, the owner of the directory, or the super-user. This feature is usefully applied to directories such as /tmp which must be publicly writable but should deny users the license to arbitrarily delete or rename each others' files.

3. The directory should be examined periodically and files older then a day should be removed. The following command can be used to do this, and should be put in a file that is periodically (one a day) executed by the cron facility:

       find /var/spool/lpd/samba -type f -mtime 2d -exec rm -f {} \;
   

   
   
   

4. You must specify the print method as printing = lprng. This will allow Samba to parse the LPRng lpq status format correctly.

5. You must put all of the printers which Samba has access to in the printcap file. Your Samba server may support reading the printcap file by using a program. In this case the printcap file entry can be one of the following:

       [printers]
         #
           printcap name = |/usr/local/libexec/filters/getpc
         # or
           printcap name = |/usr/bin/lpc client all 
       
       #!/bin/sh
       # getpc program
       /usr/bin/lpq -as | /bin/sed -e 's/[@:].*//p'
      
   

   
   
   

   The lpc client all command will generate the printcap entries for all of the printers. This was done to support Samba and other printer gateway systems. You can also use a simple script to modify the output of the printer status command as shown in the example.

6. Samba can be configured to allow guests or non-authenticated users to spool print jobs. Unfortunately, by default lpr will mark the jobs as submitted by the Samba server, not the remote users. To solve this problem, the lpr -U%U@%M option causes lpr to mark the jobs as submitted by user %U on host %M, instead of the Samba server process. The use of this option is restricted to root and a set of userids listed in the allow_user_setting configuration option. If the userid of the submitter is not in this list, then the option is quietly ignored. The -U%U@M can also be used with the other LPRng commands as well. For example:

       [printers]
           guest ok = yes
           print command =       /usr/bin/lpr  -U%U@%M -P%p -r %s
           lpq command   =       /usr/bin/lpq  -U%U@%M -P%p
           lprm command  =       /usr/bin/lprm -U%U@%M -P%p %j
           lppause command =     /usr/sbin/lpc -U%U@%M hold %p %j
           lpresume command =    /usr/sbin/lpc -U%U@%M release %p %j
           queuepause command =  /usr/sbin/lpc -U%U@%M -P%p stop
           queueresume command = /usr/sbin/lpc -U%U@%M -P%p start
   

   
   
   

2.13. Security Concerns

While the LPRng software has been written with security as the primary goal there is always the problem with undetected errors in the LPRng software that when exploited could compromise system security. The most serious concern is that of gaining ROOT (UID 0) permissions.

The simplest way to handle this problem is to not install LPRng with setuid ROOT permissions. Client programs will be able to connect to the lpd server. Since the lpd server is started by the system startup script with effective UID root, it is the only program in this suite that will have an privileged user id.

A more radical step is to run the lpd server as a non-privileged user entirely. However, the RFC1179 protocol specifies that the lpd TCP/IP port is 515 and lpd requires root permissions to open and bind to port 515. The lpd server can use the setuid() system call after binding to this port do drop ROOT capabilities. However, in order to fully compatible with RFC1179, lpd must originate connections from a reserved port in the range 721-731, although in practice port 1-1023 seems to be acceptable.

If inter-operability with non-LPRng print spoolers is not desired, then it is trivial to configure LPRng to use a non-privileged port by using the lpd.conf file. For example, in the /etc/lpd.conf file, you only need to change the indicated lines:

    # Purpose: lpd port
    #   default lpd_port=printer
    lpd_port=2000
    # or lpd_port=localhost%2000

Some legacy print filters are not meta-char-escape proof. For example, suppose that a user decided to spool a job as follows:

    h4: {66} # lpr "-J`;rm -rf /;`" /tmp/a

    J`rm -rf /;`

    /usr/local/printfilter  -J`rm -rf /;`

3.1. Solaris

The Sun Microsystems Solaris printing system is derived from the System V UNIX system. Please see the Solaris, HP, and SysVR4 Derived Systems installation information for a detailed description of how to install LPRng and remove the Solaris Print Services.

If you want to simply forward jobs from a Solaris system to a BSD print spooling system you can use the following commands to create a printer. Check your specific system references and man pages for options:

    h4: {67} # lpsystem -t bsd servername   # add server
    h4: {68} # lpadmin -p pr -s servername -T unknown -I any # set up printer
    h4: {69} # accept pr   # enable queueing
    h4: {70} # enable pr   # enable printing
    h4: {71} # lpstat -t   # show status
    scheduler is running
    system for pr: servername
    lp accepting requests since Mon Aug  6 12:00:00 PST 2000
    Printer: pr@servername  'Hp : Laserwriter' (printing disabled)
     Queue: 1 printable job
     Rank   Owner/ID                  Class Job Files                 Size Time
    1      papowell@h4+207              A   207 h4.023205                3 18:24:54

The above commands will create the necessary directories and files for the printer. If you want to use the lp -o option syntax to pass options to the LPRng print spooler you will have to enable this by hand. The /etc/printers.conf (this may be in some other directory besides /etc) needs to be modified so that it allows options to be passed using the Solaris convention, which is to put them on the S or O line of the control file. For example:

    #
    # The preferred method of modifying this file is through the use of
    # lpset(1M) or fncreate_printer(1M)
    #
    pr:bsdaddr=servername,pr,Solaris:
    _default:use=pr:

The bsdaddr=host,printer[,Solaris] indicates that the entry is for a remote RFC1179 printer on server host with name printer. The Solaris option indicates that the Solars extensions to the RFC1179 protocol are to be used.

3.2. Linux

There is no universal way to install LPRng cleanly on all of the different Linux systems. The major difficulty is the fragmentation in the various libraries, location of files, and system dependencies. If the LPRng installation procedure does not install the software correctly, please use the following remedial steps.

1. Check the LPRng web site http://www.lprng.com and see if there is a Linux Release RPM or other binary distribution for your version of Linux. If not, then you will have to do a source install.

2. Obtain the source distribution and follow the instructions outlined in other sections to compile and install the software. Use the following configuration options which correspond to Linux:

       h4: {72} # ./configure --prefix=/usr --sysconfdir=/etc --mandir=/usr/share/man
       h4: {73} # make clean all install
       h4: {74} # checkpc -f
   

   
   
   

3. You may need to modify your existing printcap file by adding the :bkf flag as shown below, or replace the entries with other filters.

       lp:\
         :if=/usr/local/libexec/lpr/hplaserjet3:\
         :bkf:\     # added to the printcap by hand
         :...
   

   
   
   

4. Test the system by printing a file. If this does not work, then you will have to determine if the problem is in the print spooling software or in the filter. See the section on ifhp for directions on how to replace the vendor supplied filters with ifhp.

3.3. AIX

This information was supplied by Dirk Nitschke, as of August 1997, and describes how to install the LPRng package on a workstation running AIX 4.1.x and possibly 3.x.x as well. Dirk would be interested in any comments or corrections.

Printing on AIX systems is different. AIX provides a general queueing facility and printing is only one way to use it. You submit a print job to a print queue using one of the commands qprt or enq. You can use the BSD or System V printing commands lpr or lp, too. The qdaemon watches all (general) queues and knows how to handle your job. A (general) queue is defined in the file /etc/qconfig. The format of this file is different from the printcap format.

OK, how to replace the AIX printing system? There is no group daemon on AIX. Therefore you have to change the default group for file ownership and process permissions or create a daemon user and group. We decided to use the printq group; on reflection it would have been easier to have created a daemon group. The user daemon exists on AIX but we have chosen lpd as the user who runs lpd and all filters and owns the spooling directories. You can change the values for group and user in your lpd.conf file or in the sources src/common/vars.c. This is an example for lpd.conf:

    # Purpose: group to run SUID ROOT programs
    #   default group=daemon
    group=printq
    # Purpose: server user for SUID purposes
    #   default user=daemon
    user=lpd

Then stop all print queues defined on your workstation. Use

    # chque -q queuename -a "up = FALSE"

If you have local printers attached to your system you will have an lpd running. Stop this daemon using SMIT (Print Spooling, Manage Print Server, Stop the Print Server Subsystem). Choosing both also removes lpd from /etc/inittab. Maybe it's faster to do this by hand:

    h4: {75} # topsrc -p'pid of /usr/sbin/lpd'
    h4: {76} # rmitab "lpd"

Now delete all print queues managed by qdaemon defined on your system. You can use SMIT for this or the commands {mk,ch,rm}que, {mk,ch,rm}quedev, {mk,ch,rm}virprt. The SMIT fast path is smit rmpq.

To start the new lpd at system startup you have to add an entry to /etc/inittab:

    h4: {77} # mkitab "lpd:2:once:/full/path/lpd"

Some work has to be done if have have a local printer attached to your workstation. You have to create a device file like /dev/lp0. The SMIT fast path for this is smit mkdev. Choose Printer/Plotter, then Printer/Plotter Devices, then Add a Printer/Plotter. To create a parallel printer device select the following:

    Plotter type:              opp Other parallel printer
    Printer/Plotter Interface: parallel
    Parent Adapter:            ppa0 Available

    Port Number: p

    Send all characters to printer UNMODIFIED   no

and select yes! We have had a lot of trouble with no. This is very important! Expect erroneous output if you choose no. If you have already created a device file, change the characteristics! SMIT's fast path is smit chdev.

Finally remove all AIX printing commands like qprt, lp, cancel, lpq, and lprm. You will find a lot of them in /usr/bin. Do not remove enq and friends if you want to use the general queueing facility.

Now you can start your new lpd.

3.4. AppleTalk Support

Netatalk is used to communicate from TCP/IP to AppleTalk printers and vice versa. The Netatalk distribution FAQ is at: http://www.umich.edu/~rsug/netatalk. Also, The University of Melbourne web site http://www.cs.mu.oz.au/appletalk/ has additional tutorial and installation information. In addition, Anders Brownworth's Web page http://thehamptons.com/anders/netatalk/ has a useful collection of information for Linux users.

The University of Michigan doesn't seem to be doing anything more for netatalk, and Adrian Sun has continued development. You'll find his updates at ftp://ftp.cobaltnet.com/pub/users/asun/testing/ He has improved netatalk considerably over the last UMich version. Documentation on netatalk is, unfortunately, almost non-existent.

There are a couple of very active mail lists for Netatalk: netatalk-admins@umich.edu and linux-atalk@netspace.org.

After you have installed and gotten netatalk working you can use the following AppleTalk configuration file to print from a Macintosh to an LPRng printer.

    Your 32 Character Printer Name:\
            :pr=|/your/path/to/lpr -Pprintername:\
            :op=username.for.printing:\
            :pd=/your/path/to/ppd/files/yourprinter.ppd:
    
    Examples:
    
    Student Printers:\
            :pr=|/usr/bin/lpr -Pstudent:\
            :op=root:\
            :pd=/var/spool/lpd/student/HP4000.PPD:
    HP 2500c:\
            :pr=|/usr/bin/lpr -Php2500c:\
            :op=root:\
            :pd=/var/spool/lpd/hp2500c/HP2500.PPD:

4.1. Overview

    +---------+    +-----+    +-----+     +--------+    +---------+
    | program | -> | lpr | -> | lpd |  -> | filter | -> | printer |
    +---------+    +-----+  * +-----+     +--------+    +---------+
                      *    *     |
                   printcap      V
                              +-----+     +--------+    +---------+
                              | lpd |  -> | filter | -> | printer |
                              +-----+     +--------+    +---------+
    
                               Figure 1

Figure 1 shows the flow of data between the individual components of the LPRng print spooling system. A program (or user) will use the lpr program to send a file to the lpd server over a TCP/IP connection. The lpd server will store the file temporarily in a spool queue directory. The information needed by the lpr and lpd programs to carry out this activity is stored in the printcap (usually called the /etc/printcap) database file.

The lpd server sorts the queue entries and determines the print order. It will select a job to be printed, open a connection to the printer, and then use a filter program to convert the file contents into a format suitable for the printer. If the file does not need conversion, then the lpd server will send the file directly to the printer.

The lpd server can also forward jobs to another print server over a network connection, optionally sending them through a filter as well. The destination server can in turn forward the job or send it to a printer.

The protocol or commands used to do this job forward and transfer are specified by RFC1179. This protocol specifies how the lpr client program sends a job to the lpd server, as well as how the lpd server forwards jobs to another server. In addition to job submission, RFC1179 specifies commands to obtain queue status, to remove jobs from the queue, and to start and stop print queues.

4.2. Sample Printcap Entry

As described in the Print Spooling Overview, the information in the printcap database is used control printing operations. While there is no RFC specifying its format or content, there is a strong de facto standard for its format. For a complete description of the printcap database see Printcap Database. For a list of all of the printcap and configuration options see Index To All The Configuration and Printcap Options.

Here is a sample printcap suitable for use by the LPRng clients:

    LPRng use :lp for destination (device and spool queue)
       lp:lp=lp@h4.private
       lpreal:lp=/dev/lp0
    
    Vintage BSD uses :rp:rm for spooler queue and :lp for device
      lp:rp=lp:rm=h4.private
      lpdev:lp=/dev/lp0

The :lp=lp@h4.private printcap entry tells the client programs that jobs for the lp printer or print queue are sent to the lp print queue queue on host h4.private. This can also be specified using the The legacy BSD :rp and :rm. The :rp=queue option specifies the print queue :rm=host option specifies the host. When both lp and :rp:rm are present the :lp option has precedence.

On the printserver the following is a sample printcap entry suitable for the lpd server:

    lp:
      :lp=/dev/lp0
      :sd=/var/spool/lpd/%P
      :filter=/usr/local/libexec/filters/ifhp

The :sd=directory option (spool queue directory) specifies the directory where print jobs will be placed. The %P will be replaced with the name of the spool queue. The :lp literal is now the path to the output device the lpd server will use to print the job. The :filter literal specifies the filter program to use to process the job before sending to the output device.

Here is another example of a printcap entry using the %P notation:

    lp:lp=%P@h4.private

4.3. Setting Up the Tutorial Configuration

The previous section has given a very high level view of printing operations and shown a sample of some printcap files. In order to do experiment with these LPRng facilities, we will need to be able to modify the printcap information and try various system configurations.

We will use a series of simple printcap entries during this tutorial. We will assume that the LPRng system is using the /etc/printcap file. If your system is configured to use another one, then you can make a symbolic link from /etc/printcap or you can simply use your default printcap file.

Save the existing printcap file and then create a new printcap file with the contents as shown below. You will need to have ROOT (superuser) permissions to change the file and perform some of the maintenance operations.

    h4: {78} # cd /etc 
    h4: {79} # mv printcap printcap.orig
    h4: {80} # vi printcap
    #  printcap file contents:
    lp:sd=/var/spool/lpd/%P
     :force_localhost
     :lp=/tmp/lp
    lp2:sd=/var/spool/lpd/%P
     :force_localhost
     :lp=/tmp/lp2
    h4: {81} # #  set permissions so everybody can read file
    h4: {82} # chmod 666 printcap

We save the original printcap file and create a new one. We give the file world writable permissions so that later we can modify this file without needing to have root permissions. The printcap file has two entries: lp and lp2. Each print queue on the server needs a spool file to hold print jobs, jobs, and the :sd value specifies its location. The %P value is replaced with the name of the printer when it is used. In classical BSD operation each host has an lpd print spooler running on the local host (we use localhost in this manual for simplicity). Files were copied to spool directories on the localhost and then then print spooler would send them to the destination, which could be another print spooler. This meant that each localhost machine had to have a print spooler and spool queue directory structure. Management of this becomes very difficult in large organizations. The force_localhost forces this mode of operation and means that the lpd server and clients must run on the same host.

We use files for the output devices (:lp=) so that we can see easily view the output (and also to save trees). We will also need to have some simple test files. Create the files using the following commands.

    h4: {83} # cp /dev/null /tmp/lp
    h4: {84} # cp /dev/null /tmp/lp2
    h4: {85} # chmod 666  /tmp/lp /tmp/lp2
    h4: {86} # echo hi >/tmp/hi
    h4: {87} # echo there >/tmp/there

We will use a dummy lpd.perms file that allows all users to do anything. This is useful for testing, but dangerous in a working environment.

    h4: {88} # #  we modify the lpd.perms to allow an ordinary user to control
    h4: {89} # mv lpd.perms lpd.perms.orig
    h4: {90} # echo "DEFAULT ACCEPT" >lpd.perms
    h4: {91} # chmod 666 lpd.perms

Finally we run checkpc to make sure that our printcap is correct and to create the necessary spool directories:

    h4: {92} # checkpc -f -V
    Checking printer 'lp'
     Checking directory: '/var/spool/lp'
       directory '/var'
       directory '/var/spool'
       directory '/var/spool/lp'
     Warning -   changing ownership '/var/spool/lp' to 1/1
       checking 'control.lp' file
       checking 'status.lp' file
       checking 'status' file
       cleaning 'status' file, 0K bytes: no truncation
       checking 'log' file
       cleaning 'log' file, 0K bytes: no truncation
       checking 'acct' file
       cleaning 'acct' file, 0K bytes: no truncation
    Checking printer 'lp2'
      Checking directory: '/var/spool/lp2'
        directory '/var'
      ....
    h4: {93} # lpc reread
    h4: {94} # lpd
    h4: {95} # lpq
    Printer: lp@h4
       Queue: no printable jobs in queue

Checkpc performs consistency checks on the printcap file and spool queue entries. The checkpc -f (fix) option will change permissions and create directories and can only be executed by ROOT. Checkpc has other functions as well - you can view printcap information, see default configuration values, and remove junk files from spool queues with it.

The lpc reread command sends a request to the lpd server to reread the configuration and printcap information. The lpd command is added as insurance in case your lpd server is not running. The exit command restores ordinary user privileges, and the lpq command is used to check that the server is running. Finally, we check to see that the lpc reread command is accepted from an ordinary user.

4.4. Restoring Original Configuration

To restore the original configuration, you simply need to restore the original printcap and lpd.perms file and then restart the lpd server. These operations require ROOT permissions.

    h4: {96} # su
    h4: {97} # cd /etc    OR    cd /usr/local/etc
    h4: {98} # mv printcap.orig printcap
    h4: {99} # mv lpd.perms.orig lpd.perms
    h4: {100} # checkpc -f
    h4: {101} # lpc reread
    h4: {102} # rm -rf /var/spool/lpd/lp /var/spool/lpd/lp2
    h4: {103} # rm -f /tmp/lp /tmp/lp2

4.5. Printing a File and Checking Status

Try the following commands. The commands appear after the prompt, and sample output that you might see is shown.

    h4: {104} % lpr -V /tmp/hi
    Version LPRng-3.6.14
    sending job 'papowell@h4+238' to lp@localhost
    connecting to 'localhost', attempt 1
    connected to 'localhost'
    requesting printer lp@localhost
    sending control file 'cfA238h4.private' to lp@localhost
    completed sending 'cfA238h4.private' to lp@localhost
    sending data file 'dfA238h4.private' to lp@localhost
    completed sending 'dfA238h4.private' to lp@localhost
    done job 'papowell@h4+238' transfer to lp@localhost

The lpr -V (Verbose) option causes lpr to print status output. As you can see from the above lines, it first tries to connect to the lpd server on host localhost, then sends a print request (which is accepted), then sends a control file containing information about the job and a data file or files which are copies of the files to be printed.

If you check the /tmp/lp file and you will find that a copy of /tmp/hi has been written to it. By default, the lpd print spooler acts as a store and forward system, accepting files to be printed, holding them in the print queue, and then forwarding them to the destination system or output device.

You can use the lpq command to view the status of the print job.

    h4: {105} % lpq
    Printer: lp@h4
     Queue: no printable jobs in queue
     Status: job 'papowell@h4+238' removed at 09:39:03.256

If you want to see more status information, use lpq -l, lpq -ll, or even lpq -L. The -L provides alL the status.

    h4: {106} % lpq -l
    Printer: lp@h4
     Queue: no printable jobs in queue
     Status: lp@h4.private: job 'papowell@h4+238' printed at 09:39:03.112
     Status: job 'papowell@h4+238' removed at 09:39:03.256
    h4: {107} % lpq -ll
    Printer: lp@h4
     Queue: no printable jobs in queue
     Status: finished 'papowell@h4+238', status 'JSUCC' at 09:39:03.108
     Status: subserver pid 8240 exit status 'JSUCC' at 09:39:03.110
     Status: lp@h4.private: job 'papowell@h4+238' printed at 09:39:03.112
     Status: job 'papowell@h4+238' removed at 09:39:03.256
    h4: {108} % lpq -L
    Printer: lp@h4
     Queue: no printable jobs in queue
     Status: subserver pid 8240 starting at 09:39:03.105
     Status: accounting at start at 09:39:03.105
     Status: opening device '/tmp/lp' at 09:39:03.105
     Status: printing job 'papowell@h4+238' at 09:39:03.106
     Status: no banner at 09:39:03.107
     Status: printing data file 'dfA238h4.private', size 3 at 09:39:03.107
     Status: printing done 'papowell@h4+238' at 09:39:03.107
     Status: accounting at end at 09:39:03.108
     Status: finished 'papowell@h4+238', status 'JSUCC' at 09:39:03.108
     Status: subserver pid 8240 exit status 'JSUCC' at 09:39:03.110
     Status: lp@h4.private: job 'papowell@h4+238' printed at 09:39:03.112
     Status: job 'papowell@h4+238' removed at 09:39:03.256

There are different status formats available as well. The lpq -s (summary) produces a single line of status per spool queue, while the lpq -v (verbose) produces output that is very suitable for processing with programs such as Perl or awk:

    h4: {109} % lpq -s
    lp@h4  0 jobs
    h4: {110} % lpq -v
    Printer: lp@h4
     Printing: no
     Aborted: no
     Spooling: no
     Queue: no printable jobs in queue
     SPOOLCONTROL=
     Status: subserver pid 8240 starting at 09:39:03.105
     Status: accounting at start at 09:39:03.105
     Status: opening device '/tmp/lp' at 09:39:03.105
     Status: printing job 'papowell@h4+238' at 09:39:03.106
     Status: no banner at 09:39:03.107
     Status: printing data file 'dfA238h4.private', size 3 at 09:39:03.107
     Status: printing done 'papowell@h4+238' at 09:39:03.107
     Status: accounting at end at 09:39:03.108
     Status: finished 'papowell@h4+238', status 'JSUCC' at 09:39:03.108
     Status: subserver pid 8240 exit status 'JSUCC' at 09:39:03.110
     Status: lp@h4.private: job 'papowell@h4+238' printed at 09:39:03.112
     Status: job 'papowell@h4+238' removed at 09:39:03.256

If you check the /tmp/lp file and you will find that a copy of /tmp/hi has been written to it. By default, the lpd print spooler acts as a store and forward system, accepting files to be printed, holding them in the print queue, and then forwarding them to the destination system or output device.

4.6. Selecting the Print Queue

In the previous section we used the default print queue. How does LPRng determine what print queue to use? First, you can explicitly specify the printer using the lpq -Pprintqueue option and the lpq -a or lpq -Pall to select all print queues:

    h4: {111} % lpq -Plp
    Printer: lp@h4
     Queue: no printable jobs in queue
    h4: {112} % lpq -Plp2
    Printer: lp2@h4
     Queue: no printable jobs in queue
    h4: {113} % lpq -a
    Printer: lp@h4
     Queue: no printable jobs in queue
    Printer: lp2@h4
     Queue: no printable jobs in queue

You can combine the lpq -a with the lpq -s option for a summary listing:

    h4: {114} % lpq -a
    Printer: lp@h4
     Queue: no printable jobs in queue
    Printer: lp2@h4
     Queue: no printable jobs in queue
    h4: {115} % lpq -s -a
    lp@h4  0 jobs
    lp2@h4  0 jobs

There is another way to explicitly specify the printqueues listed by lpq -a; see the all Printcap Entry for details.

Users can set their default printer by using the PRINTER (highest priority), LPDEST (next), NPRINTER (next), and NGPRINTER (lowest priority), environment variables. For example:

    h4: {116} % setenv PRINTER lp2
    h4: {117} % lpq
    Printer: lp2@h4
     Queue: no printable jobs in queue
    h4: {118} % unsetenv PRINTER
    h4: {119} % lpq
    Printer: lp@h4
     Queue: no printable jobs in queue

If the printer is not specified on the command line or by the environment variables, then the first printer in the printcap database will be used and then the default printer in the configuration database, and finally the compile time default. Printer and Server Information for details.

4.7. Controlling the Print Queue

The lpc command is used to examine and control the print server operation. The lpc status command displays the administrative status of a print queue. The lpd program caches status and job information in order to improve performance. The lpc flush command will flush the cached information and cause the server to regenerate it. The lpc enable and lpc disable commands enable or disable spooling to the print queue, and the lpc stop and lpc start commands stop and start printing (or transfers) of jobs in the print queue.

Let's look at the status displayed when we use these commands:

    h4: {120} % lpc status
     Printer           Printing Spooling Jobs  Server Subserver Redirect Status/(Debug)
    lp@h4               enabled  enabled    0    none    none
    h4: {121} % lpc status all
     Printer           Printing Spooling Jobs  Server Subserver Redirect Status/(Debug)
    lp@h4               enabled  enabled    0    none    none
    lp2@h4              enabled  enabled    0    none    none
    h4: {122} % lpc
    lpc>status
     Printer           Printing Spooling Jobs  Server Subserver Redirect Status/(Debug)
    lp@h4               enabled  enabled    0    none    none
    lpc>status all
     Printer           Printing Spooling Jobs  Server Subserver Redirect Status/(Debug)
    lp@h4               enabled  enabled    0    none    none
    lp2@h4              enabled  enabled    0    none    none
    lpc>quit

The lpc command can be used in command line or interactive mode as shown above. When used with no parameters it will run in interactive mode, reading one or more commands from its standard input (STDIN). The lpc status command shows the administrative status of the select print queue. The all queue name selects all print queues for display. As shown in the above example, both print queues have printing and spooling enabled and there are no jobs in the print queue. The Server and Subserver information shows if there is a process which is printing jobs, and its helper process that does the actual communication with the printer.

It might be puzzling at first why LPRng uses two processes for this operation, but the reason is very simple. Many operating system implementations have memory leaks that cause the actual process size to grow as it runs. This is especially true if a large number of databases such as the password, Domain Name Server, or other system database is consulted frequently with different queries. Since this is usually done quite a lot by the process which deals with the actual printing, the printing process would soon grow very large and then die when it could no longer obtain more memory. The Server process will fork or create a child process Subserver process that is responsible for the printing of a single job. When the job printing has been completed, the Subserver process will exit and the Server process will then create another child until there are no more jobs to be printed. The Redirect and Debug fields will be discussed in later sections.

Now let's use the basic spool queue control commands:

    h4: {123} % lpc disable
    Printer: lp@h4
    lp@h4.private: disabled
    h4: {124} % lpq
    Printer: lp@h4  (spooling disabled)
     Queue: no printable jobs in queue
    h4: {125} % lpc enable
    Printer: lp@h4
    lp@h4.private: enabled
    h4: {126} % lpq
    Printer: lp@h4
     Queue: no printable jobs in queue
    h4: {127} % lpc stop
    Printer: lp@h4
    lp@h4.private: stopped
    h4: {128} % lpq
    Printer: lp@h4  (printing disabled)
     Queue: no printable jobs in queue
    h4: {129} % lpc start
    Printer: lp@h4
    lp@h4.private: started
    h4: {130} % lpq
    Printer: lp@h4
     Queue: no printable jobs in queue

As we can see, the lpc command also reports on the status of the print queue. Let's see what happens when we print to a stopped queue:

    h4: {131} % lpc stop
    Printer: lp@h4
    lp@h4.private: stopped
    h4: {132} % lpr /tmp/hi
    h4: {133} % lpr /tmp/hi /tmp/there
    h4: {134} % lpq
    Printer: lp@h4  (printing disabled)
     Queue: 2 printable jobs
     Server: no server active
     Rank   Owner/ID                  Class Job Files               Size Time
    1      papowell@h4+17920            A 17920 /tmp/hi                 3 18:14:22
    2      papowell@h4+17922            A 17922 /tmp/hi,/tmp/there      9 18:14:30
    h4: {135} % lpc status
     Printer           Printing Spooling Jobs  Server Subserver Redirect Status/(Debug)
    lp@h4               disable  enabled    2    none    none

The lpc status shows that we have two jobs spooled. The Rank field shows the order, the Owner/ID shows the unique job ID that is assigned to the job and the Class field is the job class (this may be changed with the lpr -C class option). The Job field shows the job number assigned to this job in this particular spool queue. While the ID value never changes as a job moves through the LPRng system, the job number is specific to a particular spool queue and may change if a job is forwarded to another spool queue that has a job with the same job number. The Size field is the total number of printable bytes in the job, and the Time field shows the timestamp associated with the job.

Now let's start the print queue and watch what happens.

    h4: {136} % lpc start
    Printer: lp@h4
    lp@h4.private: started
    h4: {137} % lpq
    Printer: lp@h4
     Queue: 2 printable jobs
     Server: pid 17928 active
     Unspooler: pid 17929 active
     Status: opening device '/tmp/lp' at 18:14:43.921
     Rank   Owner/ID                  Class Job Files               Size Time
    active papowell@h4+17920            A 17920 /tmp/hi                 3 18:14:22
    2      papowell@h4+17922            A 17922 /tmp/hi,/tmp/there      9 18:14:30
    h4: {138} % lpq -ll
    Printer: lp@h4
     Queue: 2 printable jobs
     Server: pid 17928 active
     Unspooler: pid 17929 active
     Status: printing job 'papowell@h4+17920' at 18:14:43.921
     Status: no banner at 18:14:43.921
     Status: printing data file 'dfA017920h4.private', size 57 at 18:14:43.922
     Rank   Owner/ID                  Class Job Files               Size Time
    active papowell@h4+17920            A 17920 /tmp/hi                 3 18:14:22
    2      papowell@h4+17922            A 17922 /tmp/hi,/tmp/there      9 18:14:30

The Rank value of the first job has been changed to active and there is new Status information. If we use lpq -ll we can see the times that the various print operations are carried out, and details of their success or failure.

We can also use the lpc command to see the status of a particular job. We can select jobs by the user name, the ID, or the job number. For example:

    h4: {139} % lpc stop
    Printer: lp@h4
    lp@h4.private: stopped
    h4: {140} % echo hi |lpr
    h4: {141} % echo there | lpr
    h4: {142} % echo test |lpr
    h4: {143} % lpq
    Printer: lp@h4  (printing disabled)
     Queue: 3 printable jobs
     Server: no server active
     Status: job 'papowell@h4+17922' removed at 18:15:13.981
     Rank   Owner/ID                  Class Job Files               Size Time
    1      papowell@h4+17959            A 17959 (stdin)                  3 18:23:24
    2      papowell@h4+17962            A 17962 (stdin)                  6 18:23:30
    3      papowell@h4+17970            A 17970 (stdin)                  5 18:23:35
    h4: {144} % lpq 17970
    Printer: lp@h4  (printing disabled)
     Queue: 3 printable jobs
     Server: no server active
     Status: job 'papowell@h4+17922' removed at 18:15:13.981
     Rank   Owner/ID                  Class Job Files               Size Time
    3      papowell@h4+17970            A 17970 (stdin)                  5 18:23:35
    h4: {145} % lpq papowell
    Printer: lp@h4  (printing disabled)
     Queue: 3 printable jobs
     Server: no server active
     Status: job 'papowell@h4+17922' removed at 18:15:13.981
     Rank   Owner/ID                  Class Job Files               Size Time
    1      papowell@h4+17959            A 17959 (stdin)                  3 18:23:24
    2      papowell@h4+17962            A 17962 (stdin)                  6 18:23:30
    3      papowell@h4+17970            A 17970 (stdin)                  5 18:23:35
    h4: {146} % lpq -s 17970
    lp@h4  1 jobs
    h4: {147} % lpq -s papowell
    lp@h4  3 jobs
    h4: {148} % lpq -s nobody
    lp@h4  0 jobs

We use lpq -Pqueuename to select a specific print queue and lpq -a or lpq -Pall to select all queues:

    h4: {149} % lpc -a stop
    Printer: lp@h4
    lp@h4.private: stopped
    Printer: lp2@h4
    lp2@h4.private: stopped
    h4: {150} % lpc -Pall start
    Printer: lp@h4
    lp@h4.private: started
    Printer: lp2@h4
    lp2@h4.private: started

You can use the lpc command in interactive mode:

    h4: {151} % lpc
    lpc>status
     Printer           Printing Spooling Jobs  Server Subserver Redirect Status/(Debug)
    lp@h4               enabled  enabled    3    17990   17993
    lpc>status all
     Printer           Printing Spooling Jobs  Server Subserver Redirect Status/(Debug)
    lp@h4               enabled  enabled    3    17990   17993
    lp2@h4              enabled  enabled    3    none    none
    lpc>stop lp
    Printer: lp@h4
    lp@h4.private: stopped
    lpc>start lp
    Printer: lp@h4
    lp@h4.private: started
    lpc>quit

The lpc topq command can be used to put a job (or jobs) at the head of the spool queue. This command is very useful when some job requires priority service. You can select the job by using the job number or the job ID.

    h4: {152} % lpc topq lp 17970
    Printer: lp@h4
    lp: selected 'papowell@h4+17970'
    lp@h4.private: started
    h4: {153} % lpq
    Printer: lp@h4
     Queue: 3 printable jobs
     Server: pid 17999 active
     Rank   Owner/ID                  Class Job Files               Size Time
    active papowell@h4+17970            A 17970 (stdin)                  5 18:23:35
    1      papowell@h4+17959            A 17959 (stdin)                  3 18:23:24
    2      papowell@h4+17962            A 17962 (stdin)                  6 18:23:30

4.8. Job Removal

Occasionally we print a file and then change our mind and want to cancel the job. The lprm command allows us to do this.

    h4: {154} % lpq
    Printer: lp@h4  (printing disabled)
     Queue: 3 printable jobs
     Server: no server active
     Status: job 'papowell@h4+17922' removed at 18:15:13.981
     Rank   Owner/ID                  Class Job Files               Size Time
    1      papowell@h4+17959            A 17959 (stdin)                  3 18:23:24
    2      papowell@h4+17962            A 17962 (stdin)                  6 18:23:30
    3      papowell@h4+17970            A 17970 (stdin)                  5 18:23:35
    h4: {155} % lprm
    Printer lp@h4:
      checking perms 'papowell@h4+17959'
      dequeued 'papowell@h4+17959'
    h4: {156} % lpq
    Printer: lp@h4  (printing disabled)
     Queue: 2 printable jobs
     Server: no server active
     Status: job 'papowell@h4+17922' removed at 18:15:13.981
     Rank   Owner/ID                  Class Job Files               Size Time
    1      papowell@h4+17962            A 17962 (stdin)                  6 18:23:30
    2      papowell@h4+17970            A 17970 (stdin)                  5 18:23:35
    h4: {157} % lprm 17970
    Printer lp@h4:
      checking perms 'papowell@h4+17970'
      dequeued 'papowell@h4+17970'
    h4: {158} % lpq
    Printer: lp@h4  (printing disabled)
     Queue: 1 printable job
     Server: no server active
     Status: job 'papowell@h4+17922' removed at 18:15:13.981
     Rank   Owner/ID                  Class Job Files               Size Time
    1      papowell@h4+17962            A 17962 (stdin)                  6 18:23:30

By default, the lprm command removes the first job in the queue that the user has permission to remove. Also, as shown in the example, you can remove a job by specifying the job ID or the job number. If you specify a user name, you remove all of the user's jobs. This can be dangerous:

    h4: {159} % lpq
    Printer: lp@h4  (printing disabled)
     Queue: 3 printable jobs
     Server: no server active
     Status: job 'papowell@h4+17922' removed at 18:15:13.981
     Rank   Owner/ID                  Class Job Files               Size Time
    1      papowell@h4+17962            A 17962 (stdin)                  6 18:23:30
    2      papowell@h4+18499            A 18499 /tmp/hi                  3 18:56:00
    3      papowell@h4+18501            A 18501 /tmp/there               6 18:56:02
    h4: {160} % lprm papowell
    Printer lp@h4:
      checking perms 'papowell@h4+17962'
      dequeued 'papowell@h4+17962'
      checking perms 'papowell@h4+18499'
      dequeued 'papowell@h4+18499'
      checking perms 'papowell@h4+18501'
      dequeued 'papowell@h4+18501'
    h4: {161} % lpq
    Printer: lp@h4  (printing disabled)
     Queue: no printable jobs in queue
     Status: job 'papowell@h4+17922' removed at 18:15:13.981

The special user all matches all jobs in a print queue. Clearly you should be careful not to specify lprm all by accident. Even more dangerous is the following command:

    h4: {162} % lprm -a all

As you might surmise, this removes all print jobs in all queues, which is an excellent way to purge print queues of all jobs.

4.9. Print Job Filters

A printer usually understands one or more Print Job Languages. Files sent to this printer must be in one of these languages and have the appropriate job format. The most common Print Job Languages are PostScript and PCL. Text files are PCL with no special PCL control sequences.

In order for a printer to reliably print a job it needs to be reset to a known configuration and then at the end of job having it flush all of the output to the printing device. This is done by sending it start of job and end of job commands. These commands differ from printer to printer and depend on the print job language as well. Some vintage line printers also have a set of proprietary escape sequences that are used to set up margins, form size, and other printing characteristics. Usually a setup string with these escape sequences must be sent to the printer before a file can be printed.

When sending a job to the printer the print spooler will first process the job using a print job filter or filter program. This program reads the job file and then produces output in the format required for the printer.

When a print job is created the files in the print job are assigned a format. This format was meant as a guide to the print spooler and was to be used to select the filter program for the files in the job. The format was a lower case letter; the f is the default format and indicates normal processing and the l format indicates a literal or binary file. Job files that are flagged as having literal or binary format are usually passed directly to the printer or have at the most a minimal amount of processing. See Print Job Formats for more information about formats and their use with filters.

There are two ways to specify filters: the default :filter=... option and the more specific Xf=... option. The X is a lower case letter corresponding to a format. Here is a sample printcap entry with a filter specification:

    lp:sd=/var/spool/lpd/%P
      :filter=/usr/local/lib/filters/ifhp
      :rf=/usr/local/lib/filters/rfilter

We will set up a very simple filter and use it to demonstrate how filtering is done by the lpd print spooler. First, set up the /tmp/testf file as shown below.

    #!/bin/sh
    # /tmp/testf - test filter for LPRng
    PATH=/bin:/usr/bin; export PATH
    echo TESTF $0 "$@" >&2
    echo TESTF $0 "$@"
    echo ENV
    set
    echo LEADER
    /bin/cat
    echo TRAILER
    exit 0

Let us carefully examine the script line by line. The first couple of lines are boilerplate. You should always set the PATH value in a filter script or use full pathnames for executable programs. This is a good practice as it ensures that only the specified directories will be searched for commands.

The next lines echo the command line arguments to file descriptor 2 (STDERR) and to STDOUT. We will soon see how this information is displayed by the LPRng software. We then use the set command to list the shell variables to STDOUT, print LEADER to STDOUT, copy STDIN to STDOUT, and print TRAILER to STDOUT. We exit with a zero result code.

We can test our script, with the results shown below:

    h4: {163} % chmod 755 /tmp/testf
    h4: {164} % echo hi |/tmp/testf -a1
    TESTF /tmp/testf -a1
    TESTF /tmp/testf -a1
    ENV
    USER=papowell
    HOSTNAME=h4
    ...
    PATH=/bin:/usr/bin
    LEADER
    hi
    TRAILER

Let's now use this filter. Edit the lp printcap entry so it has contents indicated below, use checkpc -f to check the printcap, and then use lpc reread to restart the lpd server.

    lp:sd=/var/spool/lpd/%P
      :force_localhost
      :lp=/tmp/lp
      :filter=/tmp/testf

Execute the following commands to print the /tmp/hi file and observe the results:

    h4: {165} % cp /dev/null /tmp/lp
    h4: {166} % lpr /tmp/hi
    h4: {167} % lpq -llll
    Printer: lp@h4
     Queue: no printable jobs in queue
     Status: lp@h4.private: job 'papowell@h4+26593' printed at 21:37:21.312
     Status: job 'papowell@h4+26593' removed at 21:37:21.323
     Status: subserver pid 26683 starting at 21:39:21.908
     Status: accounting at start at 21:39:21.908
     Status: opening device '/tmp/lp' at 21:39:21.909
     Status: printing job 'papowell@h4+26681' at 21:39:21.909
     Status: no banner at 21:39:21.909
     Status: printing data file 'dfA026681h4.private', size 3, IF filter 'testf' at
    21:39:21.909
     Status: IF filter msg - 'TESTF /tmp/testf -Apapowell@h4+26681 -CA -D2000-04
    -11-21:39:21.877 -Ff -Hh4.private -J/tmp/hi -Lpapowell -Plp -Qlp -aacct -b3 -d/v
    ar/tmp/LPD/lp -edfA026681h4.private -f/tmp/hi -hh4.private -j026681 -kcfA026681h
    4.private -l66 -npapowell -sstatus -t2000-04-11-21:39:21.000 -w80 -x0 -y0 acct'
    at 21:39:21.914
     Status: IF filter finished at 21:39:22.070
     Status: printing done 'papowell@h4+26681' at 21:39:22.070
     Status: accounting at end at 21:39:22.070
     Status: finished 'papowell@h4+26681', status 'JSUCC' at 21:39:22.070
     Status: subserver pid 26683 exit status 'JSUCC' at 21:39:22.072
     Status: lp@h4.private: job 'papowell@h4+26681' printed at 21:39:22.072
     Status: job 'papowell@h4+26681' removed at 21:39:22.085
    h4: {168} % more /tmp/lp
    TESTF /tmp/testf -Apapowell@h4+26681 -CA -D2000-04-11-21:39:21.877 -Ff
    -Hh4.private -J/tmp/hi -Lpapowell -Plp -Qlp -aacct -b3 -d/var/tmp/LPD/lp
    -edfA026681h4.private -f/tmp/hi -hh4.private -j026681 -kcfA026681h4.private
    -l66 -npapowell -sstatus -t2000-04-11-21:39:21.000 -w80 -x0 -y0 acct
    ENV
    USER=papowell
    LD_LIBRARY_PATH=/lib:/usr/lib:/usr/5lib:/usr/ucblib
    HOME=/home/papowell
    PRINTCAP_ENTRY=lp
     :force_localhost
     :filter=/tmp/testf
     :lp=/var/tmp/lp
     :sd=/var/tmp/LPD/lp
    
    PS1=$
    OPTIND=1
    PS2=>
    SPOOL_DIR=/var/tmp/LPD/lp
    LOGNAME=papowell
    
    CONTROL=Hh4.private
     Ppapowell
     J/tmp/hi
     CA
     Lpapowell
     Apapowell@h4+15850
     D2000-04-26-18:13:55.505
     Qlp
     N/tmp/hi
     fdfA015850h4.private
     UdfA015850h4.private
    
    PATH=/bin:/usr/bin
    SHELL=/bin/sh
    LOGDIR=/home/papowell
    IFS=
    PRINTER=lp
    LEADER
    test Test
    TRAILER

The cp command clears out the /tmp/lp file we are using as a dummy output device. The lpr command prints the /tmp/hi file and the lpq -llll command shows the status information. The status information now contains the line that the testf script wrote to STDERR. The lpd server captures filter STDERR messages and puts it them in the spool queue status file.

As we see from the lpq status, lpd passes a large number of command line options to our filter. These options and their meanings are discussed in detail in Filter Command Line Options and Environment Variables. We will discuss these in more detail in the next section.

If we look at the /tmp/lp file, we see the command line options and values of the shell variables. For a full discussion of the environment variables passed to a filter see Filter Command Line Options and Environment Variables. The more interesting environment variables include the PRINTCAP_ENTRY variable, which is a copy of the printcap entry for this printer, and the CONTROL variable, which is a copy of the control file for the the print job.

    Hh4.private
    Ppapowell
    J/tmp/hi
    CA
    Lpapowell
    Apapowell@h4+15850
    D2000-04-26-18:13:55.505
    Qlp
    N/tmp/hi
    fdfA015850h4.private
    UdfA015850h4.private

    /tmp/testf -Apapowell@h4+26681 -CA \
       -D2000-04-11-21:39:21.877 -Ff -Hh4.private ....

    lp:sd=/var/spool/lpd/%P
      :force_localhost
      :lp=/tmp/lp
      :filter= -$ /tmp/testf '$P' $0P -X$-P ${lp} G\072 or \:

    h4: {169} % cp /dev/null /tmp/lp
    h4: {170} % lpr /tmp/hi
    h4: {171} % lpq -llll
    Printer: lp@h4
     ....
     Status: IF filter msg - 'TESTF /tmp/testf -Plp -P lp -Xlp \
        -Ylp /tmp/lp G: or :' at 01:20:21.560

    Option    Value Expansion
    $X        -X<value>
    $0X       -X <value>
    $-X          <value>
    ${name}   printcap option value if value nonzero length
    \nnn      single printable character
    $*        all options expanded using $X

    printcap:
    lp:sd=/var/spool/lpd/%P
      :force_localhost
      :lp=/tmp/lp
      :filter=/tmp/testf -F ${form}
      :form=payroll
    
    h4: {172} % cp /dev/null /tmp/lp
    h4: {173} % lpr /tmp/hi
    h4: {174} % lpq -llll
    Printer: lp@h4
     ...
     Status: IF filter msg - 'TESTF /tmp/testf -F payroll' at 09:55:31.276
     ...

    lp:sd=/var/spool/lpd/%P
      :force_localhost
      :lp=/tmp/lp
      :filter=/tmp/testf
      :bk

    h4: {175} % cp /dev/null /tmp/lp
    h4: {176} % lpr /tmp/hi
    h4: {177} % lpq -llll
    Printer: lp@h4
     ....
     Status: IF filter msg - 'TESTF /tmp/testf -Plp -w80 -l66 \
        -x0 -y0 -Ff -Lpapowell -J/tmp/hi -CA -n papowell \
        -h h4.private acct' at 08:07:46.583

    ${shell} -c "( ${if} )"

    lp:sd=/var/spool/lpd/%P
      :force_localhost
      :lp=/tmp/lp
      :filter=(echo "PREAMBLE"; /tmp/testf; echo "APPENDIX")

    h4: {178} % cp /dev/null /tmp/lp
    h4: {179} % lpr /tmp/hi
    h4: {180} % lpq -llll
    Printer: lp@h4
     ....
     Status: printing data file 'dfA018881h4.private', size 3, IF filter 'echo' at 09:22:11.476
     Status: IF filter msg - 'TESTF /tmp/testf' at 09:22:11.510
     Status: IF filter finished at 09:22:11.514

    PREAMBLE
    TESTF /tmp/testf
    ENV
    USER=papowell
    LD_LIBRARY_PATH=/lib:/usr/lib:/usr/5lib:/usr/ucblib
    ...
    PRINTER=lp
    LEADER
    hi
    TRAILER
    APPENDIX

    lp:sd=/var/spool/lpd/%P
      :force_localhost
      :lp=/tmp/lp
      :filter=(echo "PREAMBLE"; /tmp/testf $*; echo "APPENDIX")
    
    h4: {181} % lpr /tmp/hi
    h4: {182} % lpq -llll
    Printer: lp@h4
     ....
     Status: IF filter msg - 'TESTF /tmp/testf -Apapowell@h4+18941 \
       -CA -D2000-04-29-09:27:30.700 -Ff -Hh4.private -J/tmp/hi \
       -Lpapowell -Plp -Qlp -aacct -b3 -d/var/tmp/LPD/lp \
       -edfA018941h4.private -f/tmp/hi -hh4.private -j018941 -kcfA018941h4.private \
       -l66 -npapowell -sstatus -t2000-04-29-09:27:30.864 -w80 -x0 -y0 acct' at 09:27:30.879

    printcap:
      lp:sd=/var/spool/lpd/%P
        :force_localhost
        :lp=/tmp/lp
        :filter=( /tmp/testf -F '${form}' )
        :form=
    
    #!/bin/sh
    # /tmp/testf - test filter for LPRng
    PATH=/bin:/usr/bin; export PATH
    echo TESTF $0 "$@" >&2
    echo TESTF $0 "$@"
    while test $# -gt 0 ; do
      echo "PARM '$1'";
      shift;
    done
    echo LEADER
    /bin/cat
    echo TRAILER
    exit 0
    
    h4: {183} % cp /dev/null /tmp/lp
    h4: {184} % lpr /tmp/hi
    h4: {185} % lpq -llll
    Printer: lp@h4
     ...
     Status: IF filter msg - 'TESTF /tmp/testf -F' at 09:59:27.365
    
    h4: {186} % more /tmp/lp
    TESTF /tmp/testf -F
    PARM '-F'
    PARM ''
    LEADER
    hi
    TRAILER

    h4: {187} % cat /tmp/lp
    /tmp/testf -Plp -P lp -Xlp -Ylp /tmp/lp G:' at 01:20:21.560
    ENV
    CONTROL=Hh4.private
     Ppapowell
     J/tmp/hi
     CA
     Lpapowell
     Apapowell@h4+105
     D2000-04-12-15:27:26.662
     Qlp
     N/tmp/hi
     fdfA105h4.private
     UdfA105h4.private
    HOME=/home/daemon
    LD_LIBRARY_PATH=/lib:/usr/lib:/usr/5lib:/usr/ucblib
    LOGDIR=/home/daemon
    LOGNAME=daemon
    OPTIND=1
    PATH=/bin:/usr/bin:/usr/local/bin
    PRINTCAP_ENTRY=lp
     :force_localhost
     :filter=/tmp/testf
     :lp=/tmp/lp
     :sd=/tmp/LPD/lp
    PRINTER=lp
    PS1=$
    PS2=>
    SHELL=/bin/sh
    SPOOL_DIR=/tmp/LPD/lp
    USER=daemon
    
    LEADER
    hi
    TRAILER

    #!/bin/sh
    # this is an example of how to use /bin/sh and LPRng
    # to get the command line and printcap option values
    # and set shell variables from them
    #  Note that we use a couple of variables
    #PATH=/bin:/usr/bin
    Args=""
    vAr=""
    vAlue=""
    vAls=""
    iI=""
    Tf=""
    Debug=1
    if -n $Debug ; then
        set >/tmp/before
    fi
    Args="$@"
    if -n $Debug ; then
        echo "$@" >>/tmp/before
    fi
    while expr "$1" : '-.*' >/dev/null ; do
      vAr=`expr "$1" : '-\(.\).*'`;
      vAlue=`expr "$1" : '-.\(.*\)`;
      case "$vAr" in
        - ) break;;
        c ) c=1;;
        [a-zA-Z] )
          if test "X$vAlue" = "X" ; then shift; vAlue=$1; fi;
          eval $vAr='$vAlue';
          #setvar $vAr "$vAlue"
          ;;
      esac;
      shift;
    done
    
    # set shell variables to the printcap options
    #  flag   ->  flag=1
    #  flag@  ->  flag=0
    #  option=value ->  option='value'
    #
    setpcvals () {
        while test "$#" -gt 0 ; do
          iI=$1
          if expr "$iI" : " *\:" >/dev/null ; then
            vAr=`expr "$iI" : " *\:\([^=][^=]*\)=.*"`;
            vAlue=`expr "$iI" : " *\:[^=][^=]*=\(.*\)"`;
            if test "X$vAr" = "X" ; then
              vAr=`expr "$iI" : " *:\(.*\)@"`;
              vAlue=0;
            fi
            if test "X$vAr" = "X" ; then
              vAr=`expr "$iI" : " *:\(.*\)"`;
              vAlue=1;
            fi
            if test "X$vAr" != "X" ; then
              eval $vAr='$vAlue';
              #setvar $vAr "$vAlue"
            fi
          else
            vAr=`expr "$iI" : " *\([^|][^|]*\).*"`;
            if test "X$vAr" != "X" ; then
              eval Printer="$vAr"
            fi
          fi;
          shift
        done
    }
    
    # set shell variables to the printcap options
    #  flag   ->  flag=1
    #  flag@  ->  flag=0
    #  option=value ->  option='value'
    #
    setcontrolvals () {
        while test "$#" -gt 0 ; do
          iI=$1
          vAr=`expr "$iI" : " *\([A-Z]\).*"`;
          vAlue=`expr "$iI" : " *[A-Z]\(.*\)"`;
          if test "X$vAr" != "X" ; then
            eval $vAr='$vAlue';
            #setvar $vAr "$vAlue";
          fi;
          shift
        done
    }
    
    Tf=$IFS
    IFS="
    "
    setpcvals $PRINTCAP_ENTRY
    setcontrolvals $CONTROL
    IFS=$Tf
    
    #
    # restore argument list
    set -- $Args
    Args=""
    vAr=""
    vAlue=""
    vAls=""
    iI=""
    Tf=""
    
    if test -n "$Debug" ; then
        set >/tmp/after
        echo "$@" >>/tmp/after
        diff /tmp/before /tmp/after
    fi
    /bin/cat
    exit 0

    h4: {188} % cp /dev/null /tmp/lp
    h4: {189} % lpr /tmp/hi
    h4: {190} % more /tmp/lp
    0a1
    > e=dfA021771h4.private
    2a4,6
    > l=66
    > s=status
    > L=papowell
    10a15,17
    > j=021771
    > C=A
    > J=/tmp/hi
    12a20
    > a=acct
    ...
    33a58
    > Printer=lp
    ...
    hi

    #!/usr/bin/perl
    eval 'exec /usr/bin/perl -S $0 ${1+"$@"}'
        if $running_under_some_shell;
                # this emulates #! processing on NIH machines.
                # (remove #! line above if indigestible)
    
    use Getopt::Std;
    my(%args,%options);
    # get the arguments
    getopt(
        "a:b:cd:e:f:g:h:i:j:l:m:n:o:p:q:r:s:t:u:v:w:x:y:z:" .
        "A:B:C:D:E:F:G:H:I:J:L:M:N:O:P:Q:R:S:T:U:V:W:X:Y:Z:",
        \%args );
    
    # set :key=value  -> $option{$key}=$value
    # set :key@       -> $option{$key}="0"
    # set :key        -> $option{$key}="1"
     map {
        if( m/^\s*:([^=]+)=(.*)/ ){
         $options{$1}=$2;
        } elsif( m/^\s*:([^=]+)\@$/ ){
         $options{$1}="0";
        } elsif( m/^\s*:([^=]+)/ ){
         $options{$1}="1";
        } elsif( m/^\s*([^|]+)/ ){
         $options{"Printer"}=$1;
        }
     } split( "\n", $ENV{'PRINTCAP_ENTRY'});
    
    # get the control file entries
     map {
        if( m/^\s*([A-Z])(.*)/ ){
         $options{$1}=$2;
        } elsif( m/^\s*([a-z])/ ){
         $options{'Format'}=$1;
        }
     } split( "\n", $ENV{'CONTROL'});

    Hh4.private
    Ppapowell
    J/tmp/hi
    CA
    Lpapowell
    Apapowell@h4+105
    D2000-04-12-15:27:26.662
    Qlp
    N/tmp/hi
    fdfA105h4.private
    UdfA105h4.private

4.10. Job File Format Conversion with Filters

One of the major problems that face new users to UNIX printing is when they have a printer that has a proprietary print job format such as the HP DeskJet series of printers. The solution to this problem is quite simple: generate your output in PostScript, and then use the GhostScript program to convert the GhostScript output to a format compatible with your printer.

    lp:filter=/usr/local/lib/filters/myfilter:...
    
    /tmp/myfilter:
    
    #!/bin/sh
    /usr/local/bin/gs -dSAFER -dNOPAUSE -q -sDEVICE=djet500 \
        -sOutputFile=- - && exit 0
    exit 2

This simple tutorial example suffers from some serious problems. If you accidentally send a non-PostScript file to the printer GhostScript will detect this and exit with an error message but only after trying to interpret the input file as PostScript. If the input file was a text file, this can result in literally thousands of error messages and hundreds of pages of useless output.

In order to make a more robust filter we need to meet the following minimum requirements:

1. The file type should be determined, and only files that are PostScript should be passed to GhostScript.

2. We may have some conversion routines that can convert files into PostScript files and then we can send them to GhostScript for raster conversion.

3. If we cannot convert a file, then we should simply terminate the printing and cause the spooler to remove the job.

The ifhp Print Filter program is a companion to the LPRng software and does this type of operation. If you are using Linux, then you may find the RedHat Print Filters (http://www.debian.org) installed and in use on your system. The magicfilter developed by H. Peter Anvin http://www.debian.org is distributed with Debian Linux. The apsfilter by Andreas Klemm http://www.freebsd.org/~andreas/index.html is also widely used, although now most of its functionality is directly available in LPRng. Finally, the a2ps (Ascii to PostScript) converter by Akim Demaille and Miguel Santana is available from www-inf.enst.fr/~demaille/a2ps. This package provides a very nice set of facilities for massaging, mangling, bending, twisting, and being downright nasty with text or other files.

    h4: {191} % cd /tmp
    h4: {192} % echo hi >hi
    h4: {193} % gzip -c hi >hi.gz
    h4: {194} % echo "%!PS-Adobe-3.0" >test.ps
    h4: {195} % gzip -c test.ps >test.ps.gz
    h4: {196} % file hi hi.gz test.ps test.ps.gz
    hi:        ASCII text
    hi.gz:     gzip compressed data, deflated
    test.ps:   PostScript document text conforming at level 3.0
    test.ps.gz: gzip compressed data, deflated
    h4: {197} % file - <test.ps
    standard input: PostScript document text conforming at level 3.0

    #!/bin/sh
    # set up converters
    gs="/usr/local/bin/gs -dSAFER -dNOPAUSE -q -sDEVICE=djet500 \
        -sOutputFile=/dev/fd/3 - 3>&1 1>&2"
    a2ps="/usr/local/bin/a2ps -q -B -1 -M Letter --borders=no -o-"
    decompress=""
    # get the file type
    type=`file - | tr A-Z a-z | sed -e 's/  */_/g'`;
    echo TYPE $type >&2
    case "$type" in
      *gzip_compressed* ) decompress="gunzip -c |" compressed="compressed" ;;
    esac
    
    # we need to rewind the file
    perl -e "seek STDIN, 0, 0;"
    
    if test "X$decompress" != "X" ; then
        type=`$decompress head | file - | tr A-Z a-z | sed -e 's/  */_/g'`;
        echo COMPRESSED TYPE $type >&2
        # we need to rewind the file
        perl -e "seek STDIN, 0, 0;"
    fi
    case "$type" in
      *postscript* ) process="$gs" ;;
      *text* )       process="$a2ps | $gs" ;;
      * )
        echo "Cannot print type $compressed '$type'" >&2
        # exit with JREMOVE status
        exit 3
        ;;
    esac
    # in real life, replace 'echo' with 'exec'
    echo "$decompress $process"
    # exit with JABORT if this fails
    exit 2

    h4: {198} % /tmp/majik <test.ps.gz
    TYPE standard_input:_gzip_compressed_data,_deflated...
    COMPRESSED TYPE standard_input:_postscript_document_text_conforming_at_level_3.0
    gunzip -c | /usr/local/bin/gs -dSAFER -dNOPAUSE -q -sDEVICE=djet500 \
       -sOutputFile=/dev/fd/3 - 3>&1 1>&2
    h4: {199} % /tmp/majik </tmp/hi
    TYPE standard_input:_ascii_text
     /usr/local/bin/a2ps -q -B -1 -M Letter --borders=no -o- \
      | /usr/local/bin/gs -dSAFER -dNOPAUSE -q -sDEVICE=djet500 \
       -sOutputFile=/dev/fd/3 - 3>&1 1>&2

    #!/usr/bin/perl
    eval 'exec /usr/bin/perl -S $0 ${1+"$@"}'
        if $running_under_some_shell;
                # this emulates #! processing on NIH machines.
                # (remove #! line above if indigestible)
    my($gs) = "/usr/local/bin/gs -dSAFER -dNOPAUSE -q -sDEVICE=djet500 \
        -sOutputFile=/dev/fd/3 - 3>&1 1>&2";
    my($a2ps)="/usr/local/bin/a2ps -q -B -1 -M Letter --borders=no -o-";
    
    my($decompress,$compressed,$process,$type);
    $decompress=$compressed=$process=$type="";
    
    # get the file type
    $type = ` file - `;
    $type =~ tr /A-Z/a-z/;
    $type =~ s/\s+/_/g;
    print STDERR "TYPE $type\n";
    ($decompress,$compressed) = ("gunzip -c |", "gzipped")
      if( $type =~ /gzip_compressed/ );
    print STDERR "decompress $decompress\n";
    unless( seek STDIN, 0, 0 ){
        print "seek STDIN failed - $!\n"; exit 2; }
    if( $decompress ne "" ){
        $type = ` $decompress file - `;
        $type =~ tr /A-Z/a-z/;
        $type =~ s/\s+/_/g;
        print STDERR "COMPRESSED TYPE $type\n";
        unless( seek STDIN, 0, 0 ){
            print "seek STDIN failed - $!\n"; exit 2; }
    }
    $_ = $type;
    if( /postscript/ ){
        $process="$gs";
    } elsif( /_text_/ ){
        $process="$a2ps | $gs" ;;
    } else {
        print STDERR "Cannot print $compressed '$type'" >&2;
        # JREMOVE
        exit 3;
    }
    exec "$decompress $process";
    print "exec failed - $!\n";
    exit 2;

    lp:sd=/var/spool/lpd/%P
      :force_localhost
      :lp=/tmp/lp
      :ifhp=model=default
      # modify the path to ifhp appropriately
      :filter=/usr/local/libexec/filters/ifhp

    h4: {200} % cp /dev/null /tmp/lp
    h4: {201} % lpr /tmp/hi
    h4: {202} % vi /tmp/lp
    ^[%-12345X@PJL
    @PJL JOB NAME = "PID 405" DISPLAY = "papowell"
    @PJL RDYMSG DISPLAY = "papowell"
    @PJL USTATUSOFF
    @PJL USTATUS JOB = ON
    @PJL USTATUS DEVICE = ON
    @PJL USTATUS PAGE = ON
    @PJL USTATUS TIMED = 10
    @PJL ENTER LANGUAGE = PCL
    ^]E^]&^]&k2G^]&s0C^]&l0O^]9^](s0P^](s10.00H^](s4099Thi
    ^]E^]%-12345X@PJL
    @PJL RDYMSG DISPLAY = "papowell"
    @PJL EOJ NAME = "PID 405"
    @PJL USTATUSOFF
    @PJL USTATUS JOB = ON
    @PJL USTATUS DEVICE = ON
    @PJL USTATUS PAGE = ON
    @PJL USTATUS TIMED = 10
    @PJL RDYMSG DISPLAY = ""
    ^[%-12345X

    Input file:
    
      This is
      a nice day
    
    Output:
    
      This is
             a nice day

    h9: {160} % find /usr/ -type f -name lpf -print
    /usr/libexec/lpr/lpf

    lp:sd=/var/spool/lpd/%P
      :force_localhost
      :lp=/tmp/lp

    h4: {203} % cp /dev/null /tmp/lp
    h4: {204} % lpr /tmp/hi
    h4: {205} % od -bc /tmp/lp
    0000000  150 151 012
               h   i  \n
    0000003

    lp:sd=/var/spool/lpd/%P
      :force_localhost
      :lp=/tmp/lp
      # modify the path to lpf appropriately
      :filter=/usr/local/libexec/filters/lpf

    h4: {206} % cp /dev/null /tmp/lp
    h4: {207} % lpr /tmp/hi
    h4: {208} % od -bc /tmp/lp
    od -bc /tmp/lp
    0000000  150 151 015 012
               h   i  \r  \n
    0000004

    # store and forward using classical BSD :rm:rp
    lp:rp=pr:rm=host
      :sd=/var/spool/lpd/%P
      :server
    # store and forward using LPRng lp=pr@host
    lp:lp=pr@host
      :sd=/var/spool/lpd/%P
      :server

    lp:force_localhost
    lp:server
      :sd=/var/spool/lpd/%P
      :lp=lp2@localhost
    lp2:force_localhost
    lp2:server
      :sd=/var/spool/lpd/%P
      :lp=/tmp/lp2

    h4: {209} % lpr /tmp/hi
    h4: {210} % lpq -lll
    Printer: lp@h4 (dest lp2@localhost)
     Queue: no printable jobs in queue
     Status: sending control file 'cfA029h4.private' to lp2@localhost at 09:39:57.719
     Status: completed sending 'cfA029h4.private' to lp2@localhost at 09:39:57.724
     Status: sending data file 'dfA029h4.private' to lp2@localhost at 09:39:57.727
     Status: completed sending 'dfA029h4.private' to lp2@localhost at 09:39:57.925
     Status: done job 'papowell@h4+29' transfer to lp2@localhost at 09:39:57.926
     Status: subserver pid 29031 exit status 'JSUCC' at 09:39:57.953
     Status: lp@h4.private: job 'papowell@h4+29' printed at 09:39:57.961
     Status: job 'papowell@h4+29' removed at 09:39:57.993
    Printer: lp2@h4
     Queue: no printable jobs in queue
     Status: no banner at 09:39:58.054
     Status: printing data file 'dfA029h4.private', size 3 at 09:39:58.054
     Status: printing done 'papowell@h4+29' at 09:39:58.054
     Status: accounting at end at 09:39:58.054
     Status: finished 'papowell@h4+29', status 'JSUCC' at 09:39:58.054
     Status: subserver pid 29033 exit status 'JSUCC' at 09:39:58.056
     Status: lp2@h4.private: job 'papowell@h4+29' printed at 09:39:58.056
     Status: job 'papowell@h4+29' removed at 09:39:58.069

    # set /tmp/testf to contain the following
    #   and chmod 755 /tmp/testf
    #!/bin/sh
    echo TESTF $0 $@
    /bin/cat
    exit 0
    
    # printcap
    lp:force_localhost
    lp:server
      :sd=/var/spool/lpd/%P
      :lp=lp2@localhost
      :filter=/tmp/testf
      :bq_format=ffl
    lp2:force_localhost
    lp2:server
      :sd=/var/spool/lpd/%P
      :lp=/tmp/lp2

    h4: {211} % lpr /tmp/hi
    h4: {212} % lpq -llll
    h4: {213} % lpq -llll
    Printer: lp@h4 (dest lp2@localhost)
     Queue: no printable jobs in queue
     Status: no banner at 09:55:53.681
     Status: printing data file 'dfA086h4.private', size 3, IF filter 'testf' at 09:55:53.683
     Status: IF filter finished at 09:55:53.713
     Status: printing done 'papowell@h4+86' at 09:55:53.714
     Status: sending job 'papowell@h4+86' to lp2@localhost at 09:55:53.734
     Status: connecting to 'localhost', attempt 1 at 09:55:53.735
     Status: connected to 'localhost' at 09:55:53.739
     Status: requesting printer lp2@localhost at 09:55:53.740
     Status: sending control file 'cfA086h4.private' to lp2@localhost at 09:55:53.752
     Status: completed sending 'cfA086h4.private' to lp2@localhost at 09:55:53.757
     Status: sending data file 'dfA086h4.private' to lp2@localhost at 09:55:53.758
     Status: completed sending 'dfA086h4.private' to lp2@localhost at 09:55:53.939
     Status: done job 'papowell@h4+86' transfer to lp2@localhost at 09:55:53.940
     Status: subserver pid 29088 exit status 'JSUCC' at 09:55:53.980
     Status: lp@h4.private: job 'papowell@h4+86' printed at 09:55:53.983
     Status: job 'papowell@h4+86' removed at 09:55:53.998
    Printer: lp2@h4
     Queue: no printable jobs in queue
     Status: subserver pid 29092 starting at 09:55:54.005
     Status: accounting at start at 09:55:54.005
     Status: opening device '/tmp/lp2' at 09:55:54.005
     Status: printing job 'papowell@h4+86' at 09:55:54.005
     Status: no banner at 09:55:54.006
     Status: printing data file 'dfA086h4.private', size 298 at 09:55:54.006
     Status: printing done 'papowell@h4+86' at 09:55:54.006
     Status: accounting at end at 09:55:54.006
     Status: finished 'papowell@h4+86', status 'JSUCC' at 09:55:54.006
     Status: subserver pid 29092 exit status 'JSUCC' at 09:55:54.008
     Status: lp2@h4.private: job 'papowell@h4+86' printed at 09:55:54.008
     Status: job 'papowell@h4+86' removed at 09:55:54.020

4.11. Printcap Basics

In the previous sections we have used simple printcap entries to define how to set up filters and pass parameters to them. We will now examine the printcap database in more detail.

The LPRng server and client software gets their configuration information from:

• Compile time settings which set the default values for the configuration information.

• A lpd.conf file that contains values that override the compile time defaults. This information can effect the behavior of the lpd server and clients.

• Printcap entries which have configuration information for individual print queues. The information in the printcap entries for the queue override the lpd.conf and compile time defaults. The system printcap file is read first, followed by the user printcap file.

• Command line and environment variable values. These can be used to override or select particular configuration information or to select one of a set of options for use.

Each print queue or printer has a name which is used to look up the printcap information for the printer. The /etc/printcap file is the default location for the printcap information, although it can also be obtained from database servers, or generated by programs. See the Using Programs To Get Printcap Information section for details.

We will use a more complex printcap file to explore how LPRng gets the printcap information. Put the following lines in the /etc/printcap file:

    # client entry
    lp:tc=.client
    lp2:tc=.client
    .client:
      :lp=%P@localhost
      :force_localhost
    
    lp:server
      :cm=The Main Print Queue
      :lp=/tmp/lp
      :tc=.common
    
    lp2:server
      :cm=The Second Print Queue
      :lp=/tmp/lp2
      :tc=.common
    
    .common:
      :sd=/var/spool/lpd/%P
      :mx=0

    h4: {214} % lpc client
    Config
    h4: {215} % lpc client all
    Config
     :lpd_port=2000
     :printcap_path=/var/tmp/LPD/printcap
    
    Names
     :.client=.client
     :.common=.common
     :lp=lp
     :lp2=lp2
     :main=lp
    
    All
     :lp
     :lp2
    
    Printcap Information
    lp|main
     :force_localhost
     :lp=lp@localhost
    lp2
     :force_localhost
     :lp=lp2@localhost

The lpc client all command shows all of the configuration and printcap information, and is the handiest one for system debugging and diagnostics. The Name information is the names of the printcap entries that have been found in the database and is listed in sorted order. The All are entries that correspond to actual queues or printers and are listed in the order that they appear in the printcap or according to an order specified by the system administrator. (See the all Printcap Entry for details.)

    option=string value \n with escapes
    flag         # equivalent to flag=1
    flag@        # equivalent to flag=0
    option#value # equivalent to option=value

    h4: {216} % lpc server all
    Config
     :lpd_port=2000
     :printcap_path=/var/tmp/LPD/printcap
    
    Names
     :.client=.client
     :.common=.common
     :lp=lp
     :lp2=lp2
     :main=lp
    
    All
     :lp
     :lp2
    
    Printcap Information
    lp|main
     :cm=The Main Print Queue
     :force_localhost
     :lp=/tmp/lp
     :mx=0
     :sd=/var/spool/lpd/%P
     :server
    lp2
     :cm=The Second Print Queue
     :force_localhost
     :lp=/tmp/lp2
     :mx=0
     :sd=/var/spool/lpd/%P
     :server

    lp:oh=10.0.0.0/255.255.255.0,*.private,!10.0.0.10
      :lp=%P@10.0.0.10

    lp|*:cm=Wildcard Alias - %P=lp, %Q=wanted
      :lp=%P@10.0.0.10
    *:cm=Wildcard Name- %P=wanted, %Q=wanted
      :lp=%P@10.0.0.10

    lp|lp_*
      :lp=%P@10.0.0.10
    qt|qt_*
      :lp=%P@10.0.0.12

    printcap_path=|/tmp/getpc
    
    h4: {217} % cd /etc
    h4: {218} % cp lpd.conf lpd.conf.bak
    h4: {219} % echo 'printcap_path=|/tmp/getpc' >>lpd.conf

    set /tmp/getpc:
    
      #!/bin/sh
      # /tmp/getpc
      echo PROG $0 "$@" >>/tmp/trace
      cat >>/tmp/trace
      cat <<EOF
      lp:lp=test@host
      EOF
      exit 0
    
    h4: {220} % chmod 755 /tmp/getpc
    h4: {221} % echo testing | /tmp/getpc -aoption
    lp:lp=test@host
    h4: {222} % cat /tmp/trace
    PROG /tmp/getpc -aoption
    testing

    h4: {223} % lpc client all
    Config
     :lockfile=/var/tmp/LPD/lpd
     :lpd_port=2000
     :printcap_path=|/tmp/getpc
    
    Names
     :lp=lp
    
    All
     :lp
    
    Printcap Information
    lp
     :lp=test@host
    h4: {224} % cat /tmp/trace
    h4: {225} % cat /tmp/trace
    PROG /tmp/getpc -Pall -aacct -l66 -sstatus \
      -t2000-05-05-08:40:51.000 -w80 -x0 -y0 acct
    all
    PROG /tmp/getpc -Pall -aacct -l66 -sstatus \
      -t2000-05-05-08:40:51.000 -w80 -x0 -y0 acct
    *

    h4: {226} % cd /etc
    h4: {227} % cp lpd.conf.bak lpd.conf

    # remote printer - default
    lp:lp=raw@localhost
      :ifhp=model=laserjet4
      :filter=/usr/local/libexec/filters/ifhp
    # direct connection to printer over TCP/IP connection
    lp:lp=10.0.0.5%9100
      :direct
      :ifhp=model=phaser
      :filter=/usr/local/libexec/filters/ifhp

4.12. Banner Printing and the OF filter

Banner or header pages can be printed at the beginning, end, or both at the beginning or end. The following flags control how and where banners are printed. These flags are listed in order of precedence.

The pclbanner, psbanner, and lpbanner programs are part of the LPRng distribution and are usually installed in the same location as the LPRng supported filters. They produce a PCL, PostScript, or text banner respectively.

The OF filter (:of=/path) is used to process banner pages and to do any necessary setup to initialize the printer to handle banner pages. This filter has the following unusual behavior:

• It must be explicitly specified in the printcap file. It is not run by default.

  If specified, it is started at the beginning of job printing and stays present throughout the entire job printing session.

• When printing individual files, the :of filter is sent a special suspend yourself two character string, \031\001. This will cause the :of filter to send itself a SIGSUSP (suspend) signal.

• The :of filter is restarted when any information not part of a print job file, such as the initialization string (:ld option), termination string (:ld option), or form feeds at start (:fo), end (:fq), and between job files (:ff_separator), and when banners are generated by the :bp, :bs, :be, or :sb option and need to be sent to the printer.

This rather baroque behavior is mostly historical in origin, and is very much embedded in the existing documentation and methodologies of the BSD print spooling system. Originally, when a printer port was opened, a special device initialization string was sent by the printer port device driver; this usually resulted in an extra page of paper being ejected by the printer. By opening the device once and then keeping it open, the print spooler would avoid the wasted paper. The reason for suspending the :of filter was simply to save the overhead of creating an extra processes.

Unfortunately, the :of filter suspension behavior is now a problem rather than a benefit. For example, for many devices to finish printing a page correctly the filter must be closed in order for it to flush buffers and for the low level drivers to properly finish. In order to provide this functionality, the suspend_of_filter@ flag can be used. This will cause the lpd server to close the :of filters input, rather than sending it the suspend string, and to restart a new :of filter process when necessary.

4.13. Printing from lpr Directly To A Device

While the most reliable way to print is to send jobs to a print spooler, sometimes it is desirable to print directly to a printer. This method is supported by the special :direct printcap flag or the lpr -Y command line flag. The following shows the effects of this flag:

    lpr -Y -Phost%port file1 file2 ...
    Eqivalent to:
      ( for i in file1 file2 ... ; do
        $filter $i
      done ) | tcpip_connection( host%port)
    
    lpr -Y -P/dev/lp file1 file2 ...
    Eqivalent to:
      ( for i in file1 file2 ... ; do
        $filter $i
      done ) >>/dev/lp
    
    lpr -Y -P '|/program' file1 file2 ...
    Eqivalent to:
      ( for i in file1 file2 ... ; do
        $filter $i
      done ) | /program

The above examples show how we can use the command line options to send files directly to a printer. You can also create a printcap that will do the same:

    lp:direct:lp=/tmp/a:remote_support=R
    Command:
      lpr -Plp file1 file2 ...
    Equivalent to:
    lpr -P/tmp/a -Y file1 file2 ...
    
    Example:
    h4: {228} % lp -P/tmp/a /tmp/hi
    h4: {229} % cat /tmp/a /tmp/hi
    hi
    h4: {230} % lp -Plp /tmp/hi
    h4: {231} % cat /tmp/a /tmp/hi
    hi
    hi

The lpr -X filter option allows us to specify a user filter on the command line. We will use a simple example to show how this capability could be used in practice. Create the /tmp/pass file with the following contents, and give it executable permissions as shown below:

    #!/bin/sh
    # /tmp/pass file
    echo LEADER
    cat
    echo TRAILER
    exit 0

Execute the following commands to print the /tmp/hi file and observe the results:

    h4: {232} % cp /dev/null /tmp/a
    h4: {233} % lpr -P/tmp/a -X /tmp/pass /tmp/hi
    h4: {234} % cat /tmp/a
    LEADER
    hi
    TRAILER

As we see from the example, our filter has processed the input file and added the LEADER and TRAILER strings. In practice, the actual processing of the input job would be far more elaborate, and may do such things as incorporate files or other material available only on the local system. We can also use a printcap entry:

    lp:direct:lp=/tmp/a:filter=/tmp/pass
    
    h4: {235} % cp /dev/null /tmp/a
    h4: {236} % lpr -Plp /tmp/hi
    h4: {237} % cat /tmp/a
    LEADER
    hi
    TRAILER

4.14. Moving Jobs From Queue to Queue and Redirecting Queues

The lpc move command is used to move jobs in one queue to another queue on an individual basis, while the lpc redirect command redirects all incoming jobs to a new queue. Edit the printcap file so it has contents indicated below, use checkpc -f to check the printcap, and then use lpc reread to restart the lpd server.

    lp:force_localhost
    lp:server
      :sd=/var/spool/lpd/%P
      :lp=lp2@localhost
    lp2:force_localhost
    lp2:server
      :sd=/var/spool/lpd/%P
      :lp=/tmp/lp2

    h4: {238} % lpc stop lp lp2
    Printer: lp@h4
    lp@h4.private: stopped
    Printer: lp2@h4
    lp2@h4.private: stopped
    h4: {239} % lpr /tmp/hi
    h4: {240} % lpq -a
    Printer: lp@h4  (printing disabled)
     Queue: 1 printable job
     Server: no server active
     Rank   Owner/ID                  Class Job Files               Size Time
    1      papowell@h4+659              A   659 /tmp/hi                  3 08:04:03
    Printer: lp2@h4  (printing disabled)
     Queue: no printable jobs in queue
    h4: {241} % lpc move lp papowell lp2
    Printer: lp@h4
    lp: selected 'papowell@h4+659'
    lp@h4.private: move done
    h4: {242} % lpq -a
    Printer: lp@h4  (printing disabled)
     Queue: no printable jobs in queue
     Status: job 'papowell@h4+659' removed at 08:19:24.962
    Printer: lp2@h4  (printing disabled)
     Queue: 1 printable job
     Server: no server active
     Rank   Owner/ID                  Class Job Files               Size Time
    1      papowell@h4+659              A   659 /tmp/hi                  3 08:19:24

We first stop the queues so that the jobs will remain in them. We then use the lpc move fromqueue id toqueue command to select a job in the fromqueue and move it to the toqueue. A list of job numbers, job IDs, or glob patterns to match job IDs can be used to select the job.

The lpc redirect fromqueue toqueue will cause all incoming jobs to be redirected to the specified queue. You can execute the following commands and observe the results.

    h4: {243} % lpc redirect lp lp2
    Printer: lp@h4
    forwarding to 'lp2'
    lp@h4.private: redirected
    h4: {244} % lpq -a
    Printer: lp@h4  (printing disabled) (redirect lp2)
     Queue: no printable jobs in queue
    Printer: lp2@h4  (printing disabled)
     Queue: no printable jobs in queue
    h4: {245} % lpr /tmp/hi
    h4: {246} % lpq -a
    Printer: lp@h4  (printing disabled) (redirect lp2)
     Queue: no printable jobs in queue
     Status: job 'papowell@h4+935' removed at 09:08:21.410
    Printer: lp2@h4  (printing disabled)
     Queue: 1 printable job
     Server: no server active
     Rank   Owner/ID                  Class Job Files               Size Time
    1      papowell@h4+935              A   935 /tmp/hi                  3 09:08:21

To turn redirection off, use lpc redirect queue off as shown in the example below:

    h4: {247} % lpc redirect lp off
    Printer: lp@h4
    forwarding off
    h4: {248} % lpq
    Printer: lp@h4  (printing disabled)
     Queue: no printable jobs in queue
     Status: job 'papowell@h4+935' removed at 09:08:21.410

4.15. Print Job Classes, User Requested Job Priority, and Form Support

The LPRng software allows users to assign a class name to print jobs using the lpr -Cname option. This causes the lpr command to put the line Cname in the control file. By default, the (upper cased) first letter of the class name is used to assign a user requested priority to the job, with A being the default lowest priority and Z being the highest.

The ignore_requested_user_priority printcap option can be used to ignore the user requested priority and jobs will be printed in the normal first-in first-out order.

LPRng also makes use of the class information to do form support and restrict printing to a specific set of classes. By default the job class information is ignored, but the lpc class command can be used to specify one or more classes (actually glob patterns) to be printed. This facility can be used to do support printing of jobs that require a specific form setup. Here is a simple example of how to use this facility.

Edit the printcap file so it has contents indicated below, use checkpc -f to check the printcap, and then use lpc reread to restart the lpd server.

    lp:force_localhost
    lp:server
      :sd=/var/spool/lpd/%P
      :lp=lp2@localhost
    lp2:force_localhost
    lp2:server
      :sd=/var/spool/lpd/%P
      :lp=/tmp/lp2

    h4: {249} % lpc class lp red
    Printer: lp@h4
    classes printed 'red'
    lp@h4.private: class updated
    h4: {250} % lpq
    Printer: lp@h4  (classes red)
     Queue: no printable jobs in queue
    h4: {251} % lpr /tmp/hi
    h4: {252} % lpq
    Printer: lp@h4  (classes red)
     Queue: no printable jobs in queue
     Holding: 1 held jobs in queue
     Server: no server active
     Rank   Owner/ID                  Class Job Files               Size Time
    holdclass papowell@h4+82            A    82 /tmp/hi                  3 09:29:52
    h4: {253} % lpr -Cred /tmp/hi
    h4: {254} % lpq
    Printer: lp@h4  (classes red)
     Queue: no printable jobs in queue
     Holding: 1 held jobs in queue
     Server: no server active
     Status: job 'papowell@h4+89' removed at 09:30:13.569
     Rank   Owner/ID                  Class Job Files               Size Time
    holdclass papowell@h4+82            A    82 /tmp/hi                  3 09:29:52

As seen in the example, we set the queue class to red, and then sent a (default) class A job to the printer. It was not printed, and is listed with holdclass status. We sent another job which was immediately printed.

We can change the print queue class at any time, and then new class will then control what jobs are printed. To disable the class selection, use the lpc class queue off command.

    h4: {255} % lpc class lp off
    Printer: lp@h4
    all classes printed
    lp@h4.private: class updated

4.16. Holding and Releasing Jobs

The LPRng software has a wide range of facilities to hold or temporarily prevent jobs from printing. Jobs can be individually held or all jobs submitted to a queue can be held until released by an operator. Some administrators use the holdall facility and a cron script to cause jobs to be printed at specific times. The lpc holdall command causes all jobs submitted to a queue to be held until released with the lpc release command. The lpc noholdall command disables the holdall operation.

Edit the printcap file so it has contents indicated below, use checkpc -f to check the printcap, and then use lpc reread to restart the lpd server.

    lp:force_localhost
    lp:server
      :sd=/var/spool/lpd/%P
      :lp=lp2@localhost
    lp2:force_localhost
    lp2:server
      :sd=/var/spool/lpd/%P
      :lp=/tmp/lp2

Execute the following commands to print the /tmp/hi file and observe the results:

    h4: {256} % lpc holdall lp
    Printer: lp@h4
    lp@h4.private: holdall on
    h4: {257} % lpq
    Printer: lp@h4  (holdall)
     Queue: no printable jobs in queue
    h4: {258} % lpr /tmp/hi
    h4: {259} % lpq
    Printer: lp@h4  (holdall)
     Queue: no printable jobs in queue
     Holding: 1 held jobs in queue
     Server: no server active
     Rank   Owner/ID                  Class Job Files               Size Time
    hold   papowell@h4+213              A   213 /tmp/hi                  3 09:45:05
    h4: {260} % lpc release lp 213
    Printer: lp@h4
    lp: selected 'papowell@h4+213'
    lp@h4.private: started
    h4: {261} % lpq
    Printer: lp@h4  (holdall)
     Queue: no printable jobs in queue
     Status: job 'papowell@h4+213' removed at 09:45:22.570

The lpc holdall command causes all jobs to be held. We spool a job, and then use the lpc release command to release the selected job. We disable the holdall operation using the lpc noholdall command.

    h4: {262} % lpc noholdall lp
    Printer: lp@h4
    lp@h4.private: holdall off

You can also use the lpc hold command to select individual jobs in a spool queue to be held. This command is useful if there is a set of jobs which require special handling or printing at a later date. The following example shows how this command is used. We use the lpc stop and lpc start commands to simulate the normal delays in print spooling operations.

    h4: {263} % lpc stop lp
    Printer: lp@h4
    lp@h4.private: stopped
    h4: {264} % lpq
    Printer: lp@h4  (printing disabled)
     Queue: no printable jobs in queue
     Status: job 'papowell@h4+495' removed at 10:10:50.629
    h4: {265} % lpr /tmp/hi
    h4: {266} % lpr /tmp/hi
    h4: {267} % lpq
    Printer: lp@h4  (printing disabled)
     Queue: 2 printable jobs
     Server: no server active
     Rank   Owner/ID                  Class Job Files               Size Time
    1      papowell@h4+459              A   459 /tmp/hi                  3 10:40:32
    2      papowell@h4+461              A   461 /tmp/hi                  3 10:40:34
    h4: {268} % lpc hold lp 459
    Printer: lp@h4
    lp: selected 'papowell@h4+459'
    lp@h4.private: updated
    h4: {269} % lpq
    Printer: lp@h4  (printing disabled)
     Queue: 1 printable job
     Holding: 1 held jobs in queue
     Server: no server active
     Rank   Owner/ID                  Class Job Files               Size Time
    1      papowell@h4+461              A   461 /tmp/hi                  3 10:40:34
    hold   papowell@h4+459              A   459 /tmp/hi                  3 10:40:32

In the next example we show how to use the lpc hold command to select and hold an individual job. Then we start the queue and see what happens:

    h4: {270} % lpc start
    Printer: lp@h4
    lp@h4.private: started
    h4: {271} % lpq
    Printer: lp@h4
     Queue: no printable jobs in queue
     Holding: 1 held jobs in queue
     Server: no server active
     Status: job 'papowell@h4+461' removed at 10:41:24.873
     Rank   Owner/ID                  Class Job Files               Size Time
    hold   papowell@h4+459              A   459 /tmp/hi                  3 10:40:32
    h4: {272} % lpc release lp 459
    Printer: lp@h4
    lp: selected 'papowell@h4+459'
    lp@h4.private: started
    h4: {273} % lpq
    Printer: lp@h4
     Queue: no printable jobs in queue
     Status: job 'papowell@h4+459' removed at 10:41:39.457

As we see, the held job is not printed until we release it, and then is processed normally.

The printcap :ah (autohold) option has the same effect as the lpc holdall command but its actions cannot be disabled by the lpc noholdall command.

4.17. Load Balance Queues and Printer Pools

A Load Balance Queue provides a way to use multiple printers for a single print queue. All jobs are normally sent to the main or load balance queue which then dispatches the jobs to server queues or printers that do the actual printing as they become available. You can also send jobs to the individual server printers if they have special processing or setups required for a particular job. Because all of the server printers are shared by the load balance queue, they are said to be in a printer pool.

Edit the printcap file so it have the contents indicated below, create the /tmp/lp2 and /tmp/lp3 files with 0777 permissions, use checkpc -f to check the printcap, and then use lpc reread to restart the lpd server.

    # printcap
    lp:force_localhost
    lp:server
      :sd=/var/spool/lpd/%P
      :sv=lp2,lp3
    lp2:force_localhost
    lp2:server
      :ss=lp
      :sd=/var/spool/lpd/%P
      :lp=/tmp/lp2
    lp3:force_localhost
    lp3:server
      :ss=lp
      :sd=/var/spool/lpd/%P
      :lp=/tmp/lp2

The :sv=... option flags the queue as a load balance queue and lists the queues that are used for load balancing. The :ss=... option flags the queue as a server for a load balance queue and specifies the name of the load balance queue. When a job is sent to the load balance queue the lpd server checks to see which server queues are available and then the first one to become available.

Execute the following commands to print the /tmp/hi file and observe the results:

    h4: {274} % lpq
    Printer: lp@h4  (subservers lp2, lp3)
     Queue: no printable jobs in queue
     Status: job 'papowell@h4+42' removed at 07:29:57.924
    Server Printer: lp2@h4  (serving lp)
     Queue: no printable jobs in queue
    Server Printer: lp3@h4  (serving lp)
     Queue: no printable jobs in queue
    h4: {275} % lpr /tmp/hi
    h4: {276} % lpq
    Printer: lp@h4  (subservers lp2, lp3)
     Queue: 1 printable job
     Server: pid 4063 active
     Status: waiting for subserver to finish at 07:31:08.074
     Rank   Owner/ID                  Class Job Files               Size Time
    1      papowell@h4+62               A    62 /tmp/hi                  3 07:31:07
    Server Printer: lp2@h4  (serving lp)
     Queue: no printable jobs in queue
    Server Printer: lp3@h4  (serving lp)
     Queue: no printable jobs in queue
    h4: {277} % lpq
    Printer: lp@h4  (subservers lp2, lp3)
     Queue: no printable jobs in queue
     Status: no more jobs to process in load balance queue at 07:31:12.317
    Server Printer: lp2@h4  (serving lp)
     Queue: no printable jobs in queue
    Server Printer: lp3@h4  (serving lp)
     Queue: no printable jobs in queue
     Status: job 'papowell@h4+62' removed at 07:31:10.311

The first lpq command shows how the status is displayed for a load balance queue - the queue and its server queues are shown as well. Next, we use lpr to print a job (job id papowell@h4+62). We then use a couple of lpq commands to see how the job is first sent to the lp queue, which then forwards it to the lp3 queue, which then processes it and removes it. (For purposes of demonstration we have artificially slowed down the operation of the load balance queue so that the jobs will remain in the queue for sufficient time for us to display their status.) We can send another job to the load balance queue:

    h4: {278} % lpr /tmp/hi
    h4: {279} % lpq
    Printer: lp@h4  (subservers lp2, lp3)
     Queue: no printable jobs in queue
     Status: no more jobs to process in load balance queue at 07:37:17.953
    Server Printer: lp2@h4  (serving lp)
     Queue: no printable jobs in queue
     Status: job 'papowell@h4+89' removed at 07:37:15.936
    Server Printer: lp3@h4  (serving lp)
     Queue: no printable jobs in queue
     Status: job 'papowell@h4+81' removed at 07:36:40.116

This time we see that the job was put in lp2. The normal load balance queue operation is to use the server queues in round robin order.

While this simple configuration is suitable for a large number of configurations, there are situations where server queue must be chosen dynamically. For example, if the server queues are actually transferring jobs to remote clients then as soon as the job is sent to the remote client the queue appears empty and available for use. To correctly check to see if the queue is available, the status of the remote queue or destination of the server queue must be checked.

To handle this situation, a :chooser program or filter can be used. When the load balance queue is trying to decide where to send a job, it first checks the server queues to see if they are enabled for printing. If a :chooser program is specified in the load balance queue printcap entry, then it is started with the normal filter options and environment variables, supplemented as discussed below. The :chooser program will read a list of candidate queues from its STDIN, write the chosen one to its STDOUT, and then exit. The lpd server checks the :chooser exit code - if it is zero (successful) then the chosen queue is used otherwise the exit code is used for the result value of processing the job. This allows the chooser process to not only control the destination of the job but also to hold, remove, or abort the job handling process. If the :chooser does not specify a queue, then the job is skipped and another job is chosen.

One side effect of the using a chooser program is that while there are jobs that can be processed in the queue the lpd server needs to periodically check to see if a server queue has become available. If it did this continually then a very high load would be put on the system. Instead, the chooser_interval option specifies a maximum time in seconds (default 10 seconds) between the times that the lpd server checks to see if there is an available server.

Edit the printcap file so it have the contents indicated below, create the /tmp/lp2 and /tmp/lp3 files with 0777 permissions. Then create the /tmp/chooser.script with the contents indicated below, and give it 0755 (executable) permissions. Make sure that the path to the head program used in chooser.script is correct. Use checkpc -f to check the printcap, and then use lpc reread to restart the lpd server.

    # printcap
    lp:force_localhost
    lp:server
      :sd=/var/spool/lpd/%P
      :sv=lp2,lp3
      :chooser=/tmp/chooser.script
    lp2:force_localhost
    lp2:server
      :ss=lp
      :sd=/var/spool/lpd/%P
      :lp=/tmp/lp2
    lp3:force_localhost
    lp3:server
      :ss=lp
      :sd=/var/spool/lpd/%P
      :lp=/tmp/lp2
    
    # /tmp/chooser.script
    
    #!/bin/sh
    echo CHOOSER $0 $@ >>/tmp/chooser
    set >>/tmp/chooser
    /usr/bin/head -1
    exit 0

Now run the following commands:

    h4: {280} % lpr /tmp/hi
    h4: {281} % lpq -lll
    Printer: lp@h4  (subservers lp2, lp3)
     Queue: no printable jobs in queue
     Status: CHOOSER selected 'lp3' at 14:02:50.605
     Status: transferring 'papowell@h4+178' to subserver 'lp3' at 14:02:50.614
     Status: transfer 'papowell@h4+178' to subserver 'lp3' finished at 14:02:50.624
     Status: job 'papowell@h4+178' removed at 14:02:50.632
     Status: starting subserver 'lp3' at 14:02:50.632
     Status: waiting for server queue process to exit at 14:02:50.651
     Status: subserver pid 10182 exit status 'JSUCC' at 14:02:52.872
     Status: no more jobs to process in load balance queue at 14:02:52.879
    Server Printer: lp2@h4  (serving lp)
     Queue: no printable jobs in queue
    Server Printer: lp3@h4  (serving lp)
     Queue: no printable jobs in queue
     Status: waiting for subserver to exit at 14:02:50.748
     Status: subserver pid 10183 starting at 14:02:50.820
     Status: accounting at start at 14:02:50.821
     Status: opening device '/tmp/lp3' at 14:02:50.833
     Status: printing job 'papowell@h4+178' at 14:02:50.834
     Status: processing 'dfA178h4.private', size 3, format 'f', \
          IF filter 'none - passthrough' at 14:02:50.838
     Status: printing finished at 14:02:50.839
     Status: accounting at end at 14:02:50.839
     Status: finished 'papowell@h4+178', status 'JSUCC' at 14:02:50.841
     Status: subserver pid 10183 exit status 'JSUCC' at 14:02:50.843
     Status: lp3@h4.private: job 'papowell@h4+178' printed at 14:02:50.856
     Status: job 'papowell@h4+178' removed at 14:02:50.871

As you see from the example above, the CHOOSER selected lp3 for use. Let us look at the /tmp/chooser file and see how the chooser.script program was run:

    CHOOSER -Apapowell@h4+113 -CA -D2000-06-01-14:02:13.313 -Hh4.private \
       -J/tmp/hi -Lpapowell -Plp -Qlp -aacct -b3 -d/var/tmp/LPD/lp -hh4.private \
       -j113 -kcfA113h4.private -l66 -npapowell -sstatus -t2000-06-01-14:02:13.379
        -w80 -x0 -y0 acct
    USER=papowell
    LD_LIBRARY_PATH=/lib:/usr/lib:/usr/5lib:/usr/ucblib
    HOME=/home/papowell
    PRINTCAP_ENTRY=lp
     :chooser=/var/tmp/LPD/chooser
     :lp=/tmp/lp
     :sd=/var/tmp/LPD/lp
     :server
     :sv=lp2,lp3
    
    lp2=change=0x0
     done_time=0x1
     held=0x0
     move=0x0
     printable=0x0
     printer=lp2
     printing_aborted=0x0
     printing_disabled=0x0
     queue_control_file=control.lp2
     server=0
     spooldir=/var/tmp/LPD/lp2
    lp3=change=0x0
     done_time=0x2
     held=0x0
     move=0x0
     printable=0x0
     printer=lp3
     printing_aborted=0x0
     printing_disabled=0x0
     queue_control_file=control.lp3
     server=0
     spooldir=/var/tmp/LPD/lp3
    PS1=$
    OPTIND=1
    PS2=>
    SPOOL_DIR=/var/tmp/LPD/lp
    LOGNAME=papowell
    CONTROL=Hh4.private
    Ppapowell
    J/tmp/hi
    CA
    Lpapowell
    Apapowell@h4+113
    D2000-06-01-14:02:13.313
    Qlp
    N/tmp/hi
    fdfA113h4.private
    UdfA113h4.private

As you can see, the program is invoked with the same options as a normal filter. In addition, the printcap information for each server queue is passed in an environment variable with the name of the server queue. This means that if there is information needed by the chooser program to test for the availability of hardware, etc., this can be placed in the printcap information.

One of the limitations of using the :chooser program is that you may have a high overhead associated with running the program. The LPRng software provides support for linking in a user provided routine that does the same thing as the :chooser program. This routine has the following API or interface:

    Printcap Option: chooser_routine
       chooser_routine@  - default - do not use chooser routine
       chooser_routine   - use chooser routine
    
    Configuration:
       configure --with-chooser_routine=name --with-user_objs=objectfile.o
          defines the CHOOSER_ROUTINE compilation option to name
          includes the objectfile.o in the library.
    
    extern int CHOOSER_ROUTINE( struct line_list *servers,
        struct line_list *available, int *use_subserver );
      servers:    all subserver queues for this load balance queue
      available:  subserver queues to choose from
      use_subserver: chosen subserver queue
      RETURNS:
         0 - use the 'use_subserver' value as index into servers
             list for server to use
         != 0 - set job status to value returned.

See the LPRng/src/common/lpd_jobs.c and LPRng/src/common/user_objs.c files for details of the servers, available, and user_subserver parameters. The user_objs.c file provides a simple template that can be used as a starting point for a more complex routine. You should modify the code in the user_objs.c file and then use the configure options shown above to cause the user_objs.c file to be compiled and linked into the LPRng executables.

4.18. Routing Jobs To Print Queues

A routing queue is similar in concept to a load balance queue in that it transfers a job to a (different) print queue, but the job destination is chosen at the time the job is submitted to the queue rather than at the time the job is removed from the queue. A routing queue can modify the job control file, multiple copies of the same job can be sent to the same or different printers, and the job can be held, rejected, or processed immediately.

Edit the printcap file so it have the contents indicated below, create the /tmp/lp2 and /tmp/lp3 files with 0777 permissions. Create the /tmp/router.script with the contents indicated below, and give it 0755 (executable) permissions. Use checkpc -f to check the printcap, and then use lpc reread to restart the lpd server.

    # printcap
    lp:force_localhost
    lp:server
      :lp=/dev/null
      :sd=/var/spool/lpd/%P
      :router=/tmp/router.script
    lp2:force_localhost
    lp2:server
      :sd=/var/spool/lpd/%P
      :lp=/tmp/lp2
    lp3:force_localhost
    lp3:server
      :sd=/var/spool/lpd/%P
      :lp=/tmp/lp2
    
    # /tmp/router.script
    
    #!/bin/sh
    /bin/cat <<EOF
    dest lp2
    copies 2
    Cred
    end
    dest lp3
    end
    EOF
    exit 0

The router.script will write the routing information to its STDOUT. For our example, we want the destination lp2 to get two copies of the job and we want to change the class to red. Now run the following commands:

    h4: {282} % lpc stop all
    Printer: lp@h4
    lp@h4.private: stopped
    Printer: lp2@h4
    lp2@h4.private: stopped
    Printer: lp3@h4
    lp3@h4.private: stopped
    h4: {283} % lpq
    Printer: lp@h4 (dest lp@localhost) (printing disabled) (destinations lp2, lp3)
     Queue: no printable jobs in queue
    Printer: lp2@h4  (printing disabled)
     Queue: no printable jobs in queue
    Printer: lp3@h4  (printing disabled)
     Queue: no printable jobs in queue
    h4: {284} % lpr /tmp/hi
    h4: {285} % lpq
    Printer: lp@h4 (dest lp@localhost) (printing disabled) (destinations lp2, lp3)
     Queue: 1 printable job
     Server: no server active
     Rank   Owner/ID                  Class Job Files               Size Time
    1      papowell@h4+235              A   235 /tmp/hi                  3 16:14:22
     -          papowell@h4+235.1              ->lp2 <cpy 0/2>
     -          papowell@h4+235.2              ->lp3
    Printer: lp2@h4  (printing disabled)
     Queue: no printable jobs in queue
    Printer: lp3@h4  (printing disabled)
     Queue: no printable jobs in queue

The status reported for the spooled job indicates that the job is routed to lp2, and that two copies will be sent. The :destinations option in the printcap entry causes lpq to display the contents of the specified queues. Now execute the following commands:

    h4: {286} % lpc start
    Printer: lp@h4
    lp@h4.private: started
    h4: {287} % lpq
    Printer: lp@h4 (dest lp@localhost) (destinations lp2, lp3)
     Queue: no printable jobs in queue
     Status: job 'papowell@h4+235' removed at 16:14:37.491
    Printer: lp2@h4  (printing disabled)
     Queue: 2 printable jobs
     Server: no server active
     Rank   Owner/ID                  Class Job Files               Size Time
    1      papowell@h4+235.1C1          A   235 /tmp/hi                  3 16:14:36
    2      papowell@h4+235.1C2          A   236 /tmp/hi                  3 16:14:37
    Printer: lp3@h4  (printing disabled)
     Queue: 1 printable job
     Server: no server active
     Rank   Owner/ID                  Class Job Files               Size Time
    1      papowell@h4+235.2            A   237 /tmp/hi                  3 16:14:37
    h4: {288} % more /var/spool/lpd/lp2/cfA235*
    Hh4.private
    Ppapowell
    J/tmp/hi
    Cred
    Lpapowell
    Apapowell@h4+235.1C1
    D2000-06-01-16:03:25.237
    Qlp
    N/tmp/hi
    fdfA235h4.private
    UdfA235h4.private

As you can see, two copies of the job has been transferred to lp2 and one to lp3, each with a different job number, If we examine the control file for the jobs in the lp2 spool queue, we will find that the C or class information has been changed to red.

For details about all of the capabilities of the routing filter, see Dynamic Routing. Here is a summary of the information that the routing filter can put into the routing file.

The exit status of the routing filter controls how the job will be processed. If the exit code is JSUCC (0), then the job will be processed normally, JHOLD will hold the job until released, JREMOVE will remove the job, and so forth.

4.19. Job Options and the Z Control File Entry

Many printers have special capabilities such as printing in landscape mode, duplex printing, binding, or stapling. These capabilities are usually invoked or enabled by the print spooler sending special printer control commands to the printer based on values it finds in the control file. The LPRng print spooler uses the Z line in the control file to specify these options, while other print spoolers such as the Sun Microsystems Solaris lp system pass them on the S line.

Job formatting options are specified using the lpr -Z option. The lpr program concatenates the -Z options and puts them in the control file as a single Z line. For example:

    h4: {289} % lpc stop
    Printer: lp@h4
    lp@h4.private: stopped
    h4: {290} % lpr -Zthis -Zthat /tmp/hi
    h4: {291} % cat /var/spool/lp/cf*
    Hh4.private
    Ppapowell
    J/tmp/hi
    CA
    Lpapowell
    Zthis,that
    Apapowell@h4+115
    D2000-05-05-10:05:41.351
    Qlp
    N/tmp/hi
    fdfA115h4.private
    UdfA115h4.private

As we see, the Z options have been put into the control file on the Z line. The Z option values are passed to filters on the command line as the -Z command line option. These values are used by the ifhp filter to determine what control commands to send to the printer and how to format the print job output. Because each printer is different and supports a different set of capabilities it is impossible to have a set of job options supported across all printers. The following are supported by the ifhp configuration where possible. Many of these options rely on the printer supporting PostScript or having the appropriate PCL commands to do the indicated operation.

• -Zlandscape -Zportrait - select landscape or portrait orientation.

• -Zduplex -Zsimplex - select duplex (both sides of a page) or simplex (single side of a page) printing.

• -Zletter -Zlegal -Zledger -Za4 -Za5 -Zenvelope -Ztransparency - select a paper size

• -Zinupper -Zinmiddle -Zinlower - select input media from the appropriate input tray

• -Zmanual - select input from the manual feed

    landscape:lp=%P@server
    landscape:server:tc=.common
        :lp=raw@server:append_z=landscape:delete_z=portrait
    raw:server:tc=.common:lp=....
      :filter=/usr/local/libexec/filters/ifhp
    .common:sd=/var/spool/lpd/%P

    # System V to LPRng - S and O to Z options
    convert:server:tc=.common
        :lp=raw@server:prefix_option_to_option=S,O Z
    # LPRng to System V O options
    convert:server:tc=.common
        :lp=raw@server:prefix_option_to_option=Z O

    landscape:lp=%P@server
    landscape:server:tc=.common
        :lp=raw@server:append_z=landscape
    duplex:lp=%P@server
    duplex:server:tc=.common
        :lp=raw@server:append_z=duplex
    ledger:lp=%P@server
    ledger:server:tc=.common
        :lp=raw@server:append_z=ledger
    legal:lp=%P@server
    legal:server:tc=.common
        :lp=raw@server:append_z=legal
    raw:server:tc=.common:lp=....
      :filter=/usr/local/libexec/filters/ifhp
    .common:sd=/var/spool/lpd/%P

    # for clients
    pr|pr_*:lp=%Q@server
    # for server
    pr|pr_*:server
      :tc=.common:lp=....
      :incoming_control_filter=/usr/local/libexec/filters/update_z
      :filter=/usr/local/libexec/filters/ifhp
    .common:sd=/var/spool/lpd/%P

    #
    #!/usr/bin/perl
    # update_z script:
    # Determine the options according to the format of the queue name
    #  Inspired by the psfilter code of Andreas Klemm
    #  and Thomas Bueschgens 
    # First, get command line arguments
    #
    use Getopt::Std;
    my(%args,$Q,$Zopts,@file);
    getopts(
    "A:B:C:D:E:F:G:H:I:J:K:L:M:N:O:P:Q:R:S:T:U:V:W:X:Y:Z:" .
    "a:b:cd:e:f:g:h:i:j:k:l:m:n:o:p:q:r:s:t:u:v:w:x:y:z:",
    \%args );
    # read stdin
    @file = <STDIN>;
    $Zopts = "";
    # first use command line Queue name
    $Q = $args{"Q"};
    if( not $Q and (($Q) = grep(/^Q/,@file)) ){
       # next use control file Queue name
        chomp $Q if $Q;
    }
    # now we split up the name and use as parameters for Z options
    while( $Q =~ /_([^_]+)/g ){
        # you can add them or test and then add them
        if( $1 eq "landscape"
            or $1 eq "legal"
            or $1 eq "ledger" ){
            $Zopts .= ",$1"
        }
    }
    if( $Zopts ){
        # remove leading comma
        $Zopts = substr( $Zopts, 1 );
        #replace or prefix Z options
        if( not (grep { s/$/,$Zopts/ if /^Z/; } @file) ){
            print "Z" . $Zopts . "\n";
        }
    }
    print @file if( @file );
    exit 0
    
    Example Input Control file:
    
    ...
    Zover
    Qlp_landscape_ledger
    ...
    
    Modified output:
    
    ...
    Zover,landscape,ledger
    Qlp_landscape_ledger
    ...

    while( $Q =~ /_([^_]+)/g ){
        # you can add them or test and then add them
        Zopts .= ",landscape" if( $1 eq "ld" );
        Zopts .= ",ledger" if( $1 eq "11" );
        Zopts .= ",legal" if( $1 eq "15" );
        Zopts .= ",a4" if( $1 eq "a4" );
    }

4.20. Interfacing to Non-LPRng Spoolers

Given the large number of defective RFC1179 implementations that are currently in use, there will come a time when the administrator will discover that their printer with its built-in network interface, the non-UNIX based print spooler on a mainframe, or even a new print spooler on a new OS distribution will not accept jobs from the LPRng system. Usually this is caused by the presence, absence, or order of lines in the control file being sent to the remote system. To deal with this particular problem, the :bk, :control_file_line_order, :nline_after_file, and :control_filter options are used.

The :bk (BSD Kompatibility) option causes the lpd server to remove all but an extremely small subset of lines from the control file, and to put the lines in the most commonly used order. In addition it will make the control and data files names extremely short and simple. This almost always solves compatibility problems when sending jobs to older vintage print spoolers or UNIX systems.

If this does not solve the problem, then you can specify the allowed control file lines and their order using the control_file_line_order=... option. For example, control_file_line_order=CJPMD would allow only control file lines starting with C, J, P, M, and D, and this order in the control file. Note that this does not provide missing line values, it only controls line values that are present in the control file. You should also use the :bk option as well.

You might run into some really unusual implementations where the control file N (file name) information must come after the control file name. This is forced by the :nline_after_file option.

If these horrible kludges do not solve your compatibility problems then we turn to the very large hammer and edit the control file. The very last step before transfering the control file to the remote server is to filter it using the :control_filter=/path program specified in the printcap. The :control_filter reads the control file from STDIN and writes the modified control file to STDOUT. No consistency checking or validity checks are done on the new control file and the result is transferred directly to the remote system. If the :control_filter exits with a 0 status, then the normal processing continues. Any other status will cause the transfer operation to be aborted and an error reported.

4.21. Debugging, Tracing, and Log Files

The LPRng software was designed and written to provide as high a level of diagnostic information as possible. This was largely in part due to the problems with portability, coding errors, and other human frailties. Approximately 80% of the LPRng source code concerns itself with checking return values from system functions and producing error messages, debugging and tracing information, and various facilities used for regression testing and diagnosis.

The approach used by LPRng is to produce trace output for the LPRng clients or log files for the lpd server that show the various events or flow of information through the LPRng system. There are several classes or types of actions that can be traced, and various levels of trace information generated. The interface used to control these actions are the command line -D literals flags and the lpc debug command.

First, we will look at how you can use the debugging facilities for the clients. Enter the following commands:

    h4: {292} % lpr -D=
    debug usage: -D [ num | key=num | key=str | flag | flag@ | flag+N ]*
      keys recognized: network[+N,@], database[+N,@], lpr[+N,@],
       lpc[+N,@], lprm[+N,@], lpq[+N,@], test=num, job=num, log[+N,@]
    h4: {293} % lpr -V /tmp/hi
    LPRng-3.7.2, Copyright 1988-2000 Patrick Powell, <papowell@lprng.com>
    sending job 'papowell@h4+981' to lp@localhost
    connecting to 'localhost', attempt 1
    connected to 'localhost'
    requesting printer lp@localhost
    sending control file 'cfA981h4.private' to lp@localhost
    completed sending 'cfA981h4.private' to lp@localhost
    sending data file 'dfA981h4.private' to lp@localhost
    completed sending 'dfA981h4.private' to lp@localhost
    done job 'papowell@h4+981' transfer to lp@localhost
    h4: {294} % lpr -D1 /tmp/hi
    2000-06-02-09:38:08.707 h4 [13991] lpr  Get_printer: original printer '<NULL>'
    2000-06-02-09:38:08.708 h4 [13991] lpr  Get_all_printcap_entries: starting
    2000-06-02-09:38:08.708 h4 [13991] lpr  Select_pc_info: looking for 'all', depth 0
    2000-06-02-09:38:08.708 h4 [13991] lpr  Select_pc_info: returning '<NULL>'
    2000-06-02-09:38:08.708 h4 [13991] lpr  Select_pc_info: looking for '*', depth 0
    2000-06-02-09:38:08.708 h4 [13991] lpr  Select_pc_info: returning '<NULL>'
    2000-06-02-09:38:08.708 h4 [13991] lpr  Dump_line_list: Get_all_printcap_entries- \
       All_line_list - 0x8094384, coun
    ...

The lpr -D= causes the lpr (and other LPRng programs) to show what debugging flags are available. The lpr -V flag causes lpr to run in verbose mode and show its activities. Finally, we use lpr -D1 to enable the simplest level of debugging. This will produce a trace of the various activities that lpr carries out. Try lpr -D2, lpr -D3, and so forth to see the increasing amount of detail that you get.

The network and database debug flags turn on debugging for the network facilities and the database (lpd.conf, printcap, and lpd.perms) lookups. Lets see what lpr -Dnetwork shows us:

    Ch4: {295} % lpr -Dnetwork /tmp/hi
    lp: getconnection: START host localhost, timeout 10, connection_type 1
    lp: getconnection: fqdn found localhost.private, h_addr_list count 1
    lp: Link_dest_port_num: port 2000 = 2000
    lp: getconnection: sock 3, src ip 127.0.0.1, port 65209
    lp: getconnection: dest ip 127.0.0.1, port 2000
    lp: getconnection: connection to 'localhost' socket 3, errormsg 'No Error'
    lp: Link_send: host 'localhost' socket 3, timeout 6000
    lp: Link_send: str '^Blp
    ', count 4, ack 0x80447a0
    lp: Link_send: final status NO ERROR
    lp: Link_send: host 'localhost' socket 3, timeout 6000
    lp: Link_send: str '^B135 cfA276h4.private
    ', count 22, ack 0x8044370
    lp: Link_send: final status NO ERROR
    lp: Link_send: host 'localhost' socket 3, timeout 6000
    lp: Link_send: str 'Hh4.private
    Ppapowell
    J/tmp/hi
    CA
    Lpapowell
    Apapowell@h4+276
    D2000-06-02-09:44:52.369
    Qlp
    N/tmp/hi
    fdfA276h4.private
    UdfA276h4.private
    ', count 136, ack 0x8044370
    lp: Link_send: final status NO ERROR
    lp: Link_send: host 'localhost' socket 3, timeout 6000
    lp: Link_send: str '^C3 dfA276h4.private
    ', count 20, ack 0x8044310
    lp: Link_send: final status NO ERROR
    lp: Link_send: host 'localhost' socket 3, timeout 6000
    lp: Link_send: str '', count 1, ack 0x8044310
    lp: Link_send: final status NO ERROR

As we see, we get a detailed exposition of the network connection and transfer steps. If you need or want more detail, try using lpr -Dnetwork+2 or lpr -Dnetwork+3. You may want to try lpr -Ddatabase and observe the actions of the lpr program as it extracts information from the lpd.conf and printcap files. If you need or want more detail, try using lpr -Ddatabase+2 or lpr -Ddatabase+3.

If you need to trace the activities of the lpd server, it becomes a little more complex. The lpd server has a single listening process that forks and creates individual processes to handle incoming requests. Debug or diagnose the main process actions by using lpd -D.... You may also want to use lpd -F to keep the server in the foreground so you can kill it off easily. Needless to say, you should also redirect the STDERR and STDOUT so that it goes to a file so that you can examine the voluminous records at your leisure. The following shows a typical main lpd process debugging session using the C Shell.

    h4: {296} % lpd -F -D1 >&/tmp/logfile &
    [2] 14299
    h4: {297} % tail -f /tmp/logfile
    2000-06-02-09:53:39.716 h4 [14300] Waiting  Read_server_status: select status 1
    2000-06-02-09:53:39.716 h4 [14300] Waiting  Read_server_status: read status 1
    2000-06-02-09:53:39.716 h4 [14300] Waiting  Dump_line_list: Read_server_status \
       - input - 0x8047980, count 0, max 0, list 0x0
    2000-06-02-09:53:39.716 h4 [14300] Waiting  Read_server_status: select status 0
    2000-06-02-09:53:39.716 h4 [14300] Waiting  lpd: LOOP START
    2000-06-02-09:53:39.716 h4 [14300] Waiting  Get_max_servers: getrlimit returns 64
    2000-06-02-09:53:39.716 h4 [14300] Waiting  Get_max_servers: returning 32
    2000-06-02-09:53:39.716 h4 [14300] Waiting  lpd: max_servers 32, active 0
    2000-06-02-09:53:39.716 h4 [14300] Waiting  lpd: starting select timeout 'yes'
    
    ^C
    h4: {298} % jobs
    [1]  - Running                lpd -F -D1 >& /tmp/logfile
    h4: {299} % kill %1

We start the debugging session by running the lpd server in foreground mode. This causes it to send its output to STDOUT and STDERR. We redirect both of these to a file and put the lpd server in the background. Then we use tail -f to read from the log file. Finally, we kill off the lpd server.

This method is extremely difficult to use, as all of the output produced by the server and its subprocesses is sent to a single output file. If we want to debug the actions concerning a single queue, then we can use the queue log file and lpc debug command instead. The following options control debugging of an individual print queue.

The lpc debug command is used to set the debugging options in force for the spool queue. This is done by writing the debug options into the spool queue control file. Let us see how we can use this facility to trace the actions of printing a file.

Edit the printcap file so it have the contents indicated below, create the /tmp/lp and /tmp/lp2 files with 0777 permissions. Use checkpc -f to check the printcap, and then use lpc reread to restart the lpd server.

    # printcap
    lp:force_localhost
    lp:server
      :lp=/dev/null
      :sd=/var/spool/lpd/%P
      :lf=log
    lp2:force_localhost
    lp2:server
      :sd=/var/spool/lpd/%P
      :lp=/tmp/lp2
      :lf=log

Now execute the following commands:

    h4: {300} % lpq
    Printer: lp@h4
     Queue: no printable jobs in queue
    h4: {301} % lpc debug lp 1
    Printer: lp@h4
    debugging override set to '1'
    lp@h4.private: updated
    h4: {302} % lpc status
     Printer           Printing Spooling Jobs  Server Subserver Redirect Status/(Debug)
    lp@h4               enabled  enabled    0    none    none          (1)
    h4: {303} % lpr /tmp/hi
    h4: {304} % more /var/spool/lpd/lp2/log
    2000-06-02-10:10:50.589 h4 [14496] (Server)  lp: Update_spool_info: printer 'lp'
    2000-06-02-10:10:50.590 h4 [14496] (Server)  lp: Do_queue_jobs: printable 1, held 0, move 0
    2000-06-02-10:10:50.590 h4 [14496] (Server)  lp: Do_queue_jobs: after Scan_queue next fd 5
    2000-06-02-10:10:50.590 h4 [14496] (Server)  lp: Do_queue_jobs: MAIN LOOP
    2000-06-02-10:10:50.590 h4 [14496] (Server)  lp: Do_queue_jobs: Susr1 before scan 0
    2000-06-02-10:10:50.591 h4 [14496] (Server)  lp: Do_queue_jobs: chooser '<NULL>', chooser_routine 0

The lpc debug command sets the debug level to 1. We can use the lpc status command to see what debug flags or actions are currently specified for the spool queue. We then send a job to the spool queue and examine the log file contents.

Each line in the log file has a timestamp, the name of the host, the process id that produced it, and a heading that tells the action or activity that the process is performing, and the name of the print queue that is being processed and a trace message. By convention, the trace message lists the name of the routine that processed it and then the actual information. Some messages may extend over several lines, but each line has the standard header at the start of the line.

The default debug or trace actions were designed to trace problems with printing, as these are the most common. However, you can also use the lpr, lpc, lprm, or lpq option to cause the lpd server to trace the actions during the execution of an lpr, lpc, lprm, or lpq request.

The log option is used to test various logging facilities and is usually not used for general purpose debugging.

5.1. Printer and Server Information

Options used:

• PRINTER, LPDEST, NPRINTER NGPRINTER Environment variables

• force_localhost FLAG force clients to send requests to localhost

When an LPRng client such as lpr, lpq, lprm, or lpc needs to communicate with a print server, the only information they normally need is:

1. The remote printer (:rp) value to be used in requests to the lpd print server. This is sometimes referred to as the printer or print queue name.

2. The remote server (:rm) which is the The IP address or hostname of the print server.

3. The original queue name specified by the user which may be used as part of the job information sent to the print server.

LPRng has several ways to specify the printer queue and server information.

5.2. Command Line -Pprinter@host

The -P printer@host literal explicitly provides a printer and server value. This is equivalent to the printcap entry shown below:

    lpr -Plaser@10.0.0.1
      equivalent to printcap entry:
        laser:lp=laser@10.0.0.1
    lpq -Plp@myserver
      equivalent to printcap entry:
        lp:lp=lp@myserver

5.3. Command Line -Pprinter

Use the printcap entry with the name or alias printer and use the information in that printcap entry. Example:

    lpr -Plp
      look up printcap entry for 'lp'

5.4. PRINTER, LPDEST, NPRINTER, and NGPRINTER Environment Variables

If no command line option is specified, the LPRng clients will use the first defined PRINTER, LPDEST, NPRINTER, or NGPRINTER environment variable value and will use the value as though specified as a -P$PRINTER command line literal. If the value has the form -Pprinter@host the print queue will be printer on server host and not consult the printcap database. If the value has the form printer then the printcap will be searched for a printer printcap entry. For example:

    export PRINTER=laser@10.0.0.1; lpr
      equivalent to printcap entry:
        laser:lp=laser@10.0.0.1
    export PRINTER=pr; lpr
      look up printcap entry for 'lp'

5.5. Wildcard Printcap Entry

If you specify a printcap name or alias as * (wildcard), then if the LPRng system cannot find a printcap with the exact name then the first matching wildcard will be used. For example:

    pr|*:rm=server
      lpr -Ppr2 will match, and result in a printcap entry
        pr|pr2:rm=server
    
    *|pr:rm=server
      lpr -Ppr2 will match, and result in a printcap entry
        pr2|pr:rm=server

5.6. First Printcap Entry

If you do not specify a printer on the command line or in the environment variables, then LPRng will search the printcap and use the first valid printcap entry as the printer. It will use the first one found as the default.

5.7. Default Printer and Server Host

Options used:

• default_remotehost=default rm (remote host)

• default_printer=default rp (remote printer)

If the preceding steps do not yeild a printer, then the default_printer and default_remote_host values from the lpd.conf configuration file will be used. If there is no configuration file, then the compile time defaults will be used.

Using the fallback values is usually not a desirable event and may indicate that you have a misconfigured host, so the compile time defaults are usually set to missingprinter@localhost to provide an annoying message for users.

5.8. Force Connection to Localhost

Options used:

• force_localhost FLAG force localhost to be remote host

The legacy BSD print spooler required an lpd print server to be running on each host. During the initial stages of development and deployment, the default LPRng configuration and deployment was to always allow lightweight operation, that is, clients would always connect to the remote host specified in the printcap.

While this default was appropriate for experienced system administrators, novice administrators or those who had already configured print spooling systems and simply wanted to upgrade found themselves confused by this change. This problem resulted in over 700 postings to the LPRng mailing list in a five year period.

This problem was solved by providing a force_localhost option in the configuration, and setting the default value to 1 or TRUE. When this option is TRUE, then all LPRng clients will connect to the server on the localhost, unless they use the lpr -Pserver@host command line form. If lightweight operation is wanted, the administrator can either compile the LPRng software with the appropriate value or can explicitly set the force_localhost@ flag.

    # default:
    lp:lp=lp@10.0.0.1:...
      lpr -Plp ->
        lp:lp=lp@localhost:...
      lpr -Plp@10.0.0.1 ->
        lp:lp=lp@10.0.0.1  (no other options)
    
    lp:lp=lp@10.0.0.1:force_localhost@:...
      lpr -Plp ->
        lp:lp=lp@10.0.0.1:...
    
    To disable at compile time:
      configure --disable-force_localhost

5.9. User Identification

Options used:

• allow_user_setting=privileged users

When an client program sends a command to the lpd server it may need to provide the name of the user who is originating the request for service. This name is obtained by looking up the UID of the user running the client in the appropriate user information database; if the information is not found the UID is used instead. Also, the client machine hostname may also be needed. This is usually determined by using a DNS lookup and trying to determine if there is a canonical or Fully Qualified Domain Name for the host and using this.

The lpr -U name@host (and for lpq, lprm, and lpc) option allows privileged users to cause the client software to use the name value as the originator and host as the machine name. This allows privileged users to impersonate other users. This is most useful for programs such as Samba and PCNFS, which need to act as proxies for users.

By default, ROOT (UID 0) is the only user that can masquerade as another user. The allow_user_setting=name,name... configuration option can be used to specify a list of names or UIDs that can also perform masquerading. For example, if the Samba server was running as user samba, then allow_user_setting=samba would allow it to specify the name of print job originator as a remote user, and the remote user would not need a login account on the system.

6.1. Job Format Options

Options used:

• default_format=default print job format (f)

• fx=supported formats for printing

The legacy or vintage BSD print spooling system assigned each job a format. This format was used by the lpd server to select an appropriate filter program that would process the job and format it correctly for the printer. By convention, lower case letters were used to specify job formats.

The LPRng lpr client supports the legacy or vintage BSD formats, and also provides the -Fx literal to allow addition formats to be specified. If a format is specified the default_format value (usually f) is used. The fx=... option value is a list of the (lower case) characters corresponding to the formats allowed for a spool queue. For example, fx=flv would allow only jobs with format f, l, or v to be spooled to a queue. By default, all job formats are allowed.

A couple of job formats that require special treatment: the b (binary) and its alias the l (literal) format, and the p (pretty print) format. The -b or -l command line literal will select job format l (literal) for the job. By default, jobs marked with l format are supposed to have a minimum amount of handling and passed directly to a printer. The p (pretty print) format is just the opposite - these jobs are supposed to be pretty printed according to the various facilities available to the lpd print spooler.

6.2. Job Pretty Printing, Banners, Priority, and Accounting

Options used:

• ab FLAG always print banner

• sh FLAG suppress header (banner)

The legacy or vintage BSD pretty printing facility support allowed users to specify the title (-T title), indentation (-i indent), width (-i indent) of output for pretty printing. These probably will not have any effect, but their values are placed in the control file and sent to the lpd server.

The job name (-J name) and no banner page (-h) literals also cause information to be placed in the control file. The -J value is used to specify a job name on a banner page, and is placed in the control file. The -h (no header) has the strange effect of not putting banner name information in the control file. Apparently, if you do not have a name for your banner then no name will be sent.

If the :sh option is explicitly specified in a printcap entry for the lpr client, then it has the effect of the -h literal. However, the :ab (Always Print Banner) option can be used on the print server to always force a banner to be printed even if the user does not specify a banner.

Finally, the -R literal allows additional accounting information to be placed in the control file.

6.3. Job Class and Priority

Options used:

• break_classname_priority_link FLAG classname does not set priority

• default_priority=default priority

• ignore_requested_user_priority FLAG ignore requested user priority

The -Cclass information is used placed in the control file; the default class and priority is set by the default_priority option (default A). The first letter of the class information is uppercased and then used as the job priority.

The break_classname_priority_link option causes lpr to place class information in the control file but not to use it to set the job priority. This is usually used in institutions where users should not specify their priority. Finally, the ignore_requested_user_priority is actually used by lpd to ignore the priority requested by users.

6.4. Job Copies and Job Size

Options used:

• mc=maximum number of copies

• mx=maximum job size (Kbytes)

The :mc (maximum number of copies) and :mx (maximum job size) options are used by both the lpr and lpd programs. The lpr -Kn or lpr -#n option sets the numbers of copies wanted to n; if this is larger than the :mc value then the lpr client will not print the job and the lpd server will discard the job with an error. The job size is the product of the number of copies and the sum of the individual file sizes. This is, in effect, the total number of bytes to be transferred to the printer. If the job size is larger than the :mx limit, then the lpr client will not print the job and the lpd server will discard the job with an error.

6.5. Job Completion Notification Requested

Options used:

• allow_user_logging FLAG users can send status

• lpr_bsd FLAG lpr -m acts as legacy BSD flag

The lpr -m mailaddr option will put the specified mailaddr value into the control file. How this is processed is left to the particular server implementation. See the Abnormal Termination section for details.

LPRng extends the lpr -m mailaddr to allow mail addresses of the form host[%port][/(TCP|UPD)], and when the job is being transferred or printed the lpd server to open a connection to the specified TCP/IP address and send job progress information. This is a security loophole and the allow_user_logging flag must be present to allow this operation.

The lpr_bsd will cause the lpr -m option not to take an argument, as in the BSD lpr, and will place the users name and host information in the control file as the destination for notification.

6.6. Remove Files After Spooling

The lpr -r option is extremely dangerous and has proven to be fatal to a large number of system administrators, so it should be used with caution. Unfortunately, it is used in a large number of shell scripts and by default in a vast number of programs so it is present in the LPRng software.

Its action is quite simple. After sending the print job to the spooler, it will try to unlink the original files. It will do the unlinking operation as the original user, but if the original user had permissions to remove, say, /etc/password, then the file will be removed.

6.7. The -Z Passthrough to Filter Options

Options used:

• append_z=Append values to Z options list

• prefix_z=Prefix values to Z options list

• remove_z=Remove values from Z options list

• prefix_s_to_z FLAG Prefix control file S to Z information

• prefix_s_to_z FLAG Prefix control file Z to S information

By convention all of the values specified with the lpr -Z option are placed in the job control file and passed to the lpd server, which turn passes them to the print filters. This allows users to pass options that are not part of the RFC1179 repetoire to filters.

In addition to this simple method of providing options, we can have the lpr and lpd systems add options to the control file information. The prefix_z and append_z options allow us to put Z options at the start or end of the user provided list; the remove_z removes specified options from the list.

The prefix_s_to_z and prefix_z_to_s options are usually used by the lpd server, and provides a simple way to have the SystemV lp -o option values put into the Z options value. This is very useful when existing SysV lp print spooling systems need to be interfaced to LPRng and the options need to be handled in a meaningful manner. The prefix_z_to_s is similarly used when you want to forward jobs to a SysV spooling system and have the options passed correctly.

If present in the printer configuration, the various requested actions are are done by the lpr client, the lpd server on job reception, and the lpd server again on job processing. This redundancy ensures that jobs which are sent to this queue, arrive at this queue, or are processed by this queue have the options set appropriately.

6.8. Record Queue Name in Control File

Options used:

• qq FLAG Insert queue name into control file

• force_queuename=Queuename to be used

The :qq use queuename option tells LPRng to record the queue name that a job was originally queued to in the control file as the Q information. The force_queuename=... entry forces the queue name to be the specified value. For example, the following printcap entry and lpr commands will result in a filter being passed the arguments shown below.

    #printcap
      pr1_landscape|pr1_portrait|pr_raw
       :filter=/.../filter
       :lp=/dev/pr
       :qq
    
    lpr -Ppr1_landscape      lpr -Ppr1_portrait
      control file -
        Qpr1_landscape          Qpr1_portrait
    
    filter command line:
      ... -Qpr1_landscape     ... -Qpr1_portrait

The force_queuename can be used for force a specific value into the control file Q information.

    john|tom|frank
      :filter=/.../filter
      :lp=/dev/pr
      :force_queuename=office
    
    lpr -Pjohn
      control file -
       Qoffice
    
    filter command line:
      ... -Qoffice

6.9. Check For Nonprintable File

Options used:

• check_for_nonprintable FLAG lpr checks for non-printable file

• ml=minimum number of printable characters

By default lpr does not check files for for non-printable characters (i.e., escape characters) at the start of the print file. You can set the check_for_nonprintable flag to cause it to do so. The :ml value specifies the number of characters that are to be checked. Clearly, if it is 0, none will be checked.

6.10. Job Filtering By LPR

Options used:

• lpr_bounce FLAG lpr does filtering

Some users would like the advantages of the filtering and processing capabilities of a lpd daemon without running a lpd daemon on their system. By having the lpr program process the job by passing it through the various filters and then send the output of the filters as the print job you can get the desired effect.

    # Simple example of an lpr_bounce entry
    bounce
      :lpr_bounce
      :lp=lp@remote
      :filter=/usr/local/bin/lpf

The lpr_bounce flag, if present in the printcap entry, will force lpr to process the job using the specified filters and send the outputs of the filters to the remote printer for further processing.

6.11. Restrict Queue Use to Group Members

Options used:

• rg=Restricted group list

The :rg value specifies a list of groups. If this value is present use of a printer or operation is restricted to only users in a particular group. This check is done by both the lpr client and the lpd server if the option is present.

6.12. Fixing Bad Control Files and Metacharacters

Options used:

• safe_chars=additional safe characters for control file

RFC1179 defines a simple protocol and standard for print jobs to be interchanged between print spooling systems. Unfortunately, there were some major mistakes in not specifying the exact form that text would take when placed in the control file.

By default, LPRng will brutally convert a non-conforming RFC1179 control file into one that is acceptable to most, if not all, existing RFC1179 implementations. In order to prevent problems with LPRng ruthlessly purges all characters but upper and lower case letters, spaces, tabs, and -_.@/:()=,+-% from the control file, replacing suspicious characters with underscore (_). In addition, LPRng will ruthlessly regenerate control file entries and data file names so that they are compliant with all known RFC1179 implementations.

For some installations, the default set of safe characters may be overly restrictive. For example, vintage software may generate files with # characters in the J line of the control file. The replacement of this character by underscore (_) may cause other applications which use the control file information to stop working. The :safe_chars option allows the user to specify an additional set of safe characters in the lpd.conf configuration file(s).

For example, :safe_chars=#" would allow the # and " characters to appear in the control file.

6.13. Minimum Spool Queue Free Space

Options used:

• minfree=Size in Kbytes

If this value is non-zero, then the lpd receiving server checks to see that there is the specified number of Kbytes of file space available before accepting a job. If there is not enough space then the job is rejected.

6.14. FQDN Host Information

Options used:

• force_fqdn_hostname FLAG Update control file with FQDN name

• use_shorthost FLAG short control and data file names

Some lpr clients do not put a FQDN host name in their control file. The force_fqdn_hostname flag will cause lpd to put a FQDN host name in the control file. This option will assume that the domain is where the connection originated from.

Some systems cannot handle FQDN hostnames in control and data file formats. The use_shorthost option will send control and data files with very short names to the remote print server.

7.1. lpq Queue Selection (lpq -Pprinter, lpq -a)

If no queue is specified, then the default queue is used, with -Pprinter@host causing a direct connection to the named host. The -a literal selects all queues.

7.2. lpq Job Selection

Jobs are selected by providing a job number, or glob pattern that is matched to the user name and and job identifier. If multiple patterns are provided each is applied in turn against the jobs in a queue until all have been tried. If any one of the patterns match then the job status is displayed.

If no selection information is provided or the all pattern is provided then all jobs in the queue are displayed.

7.3. lpq Short Format (lpq -s)

This is one line per spool queue:

    % lpq -sa
    t1@astart110  (printing disabled) 1 job
    t2@astart110  (routed/bounce to t1@h10.private) 0 jobs
    t3@astart110  (forwarding to t3a@h10.private)
    t3a@astart110  (forwarding to t2@h10.private)
    t4@astart110  (subservers t5, t6)  0 jobs
    t5@astart110  (serving t4) 0 jobs
    t6@astart110  (serving t4) 0 jobs

Note that the name of the printer/host is first, followed by optional status information, followed by the number of jobs. Only printcap entries with spool queues have a jobs word in the last position. The -a literal forces status for all queues or the queues in the all printcap entry to be returned.

The stalled_time (default 120 seconds) printcap option can be used to set a time after which active jobs will be reported as stalled.

7.4. lpq Long Format (lpq, lpq -l, lpq -L)

This is the default status display. It is a nicely formatted, extremely verbose format that is suitable for humble human interpretation. For example:

    % lpq -a
    Printer: t1@astart110  'Test Printer 1' (printing disabled)
     Queue: 1 printable job
     Server: no server active
     Status: finished operations at 09:44:00
     Rank   Owner/ID                   Class Job  Files             Size Time
    1       papowell@lprng110+202228663    A 10663 /tmp/hi               3 20:22:29
    Printer: t2@astart110  'Test Printer 2' (routed/bounce to t1@h10.private)
     Queue: no printable jobs in queue
     Status: finished operations at 16:30:08
    Printer: t3@astart110  (forwarding to t3a@h10.private)
    Printer: t3a@astart110  (forwarding to t2@h10.private)
    Printer: t4@astart110  (subservers t5, t6)
     Queue: no printable jobs in queue
     Status: finished operations at 09:44:06
    Server Printer: t5@astart110  (serving t4)
     Queue: no printable jobs in queue
     Status: finished operations at 09:44:06
    Server Printer: t6@astart110  (serving t4)
     Queue: no printable jobs in queue
     Status: finished operations at 09:10:00

The lpq -l (longer information) option causes more of the status information to be printed. You can use increasing numbers of lpq -l options ( lpq -ll also works) to get more status. Use lpq -L for the maximum amount of status information.

7.5. lpq Verbose Format (lpq -v)

This uses an extension to the RFC1179 protocol, and is supported only by LPRng. The amount of information displayed is the brutal, and in effect does a total database dump of the LPD. This has been developed in order to provide diagnostic and status information for databases that need to keep track of job progress through a spool queue.

    % lpq -v
    Printer: t1@astart110
     Comment: Test Printer 1
     Printing: no
     Spooling: yes
     Queue: 1 printable job
     Server: no server active
     Status: accounting at end 'papowell@lprng110+094352860' at 09:44:00
     Status: printing 'papowell@lprng110+094352860', closing device at 09:44:00
     Status: printing 'papowell@lprng110+094352860', finished  at 09:44:00
     Status: subserver status 'JSUCC' for 'papowell@lprng110+094352860' \
                on attempt 1 at 09:44:00
     Status: finished operations at 09:44:00
     Job: papowell@lprng110+202228663 status= 1
     Job: papowell@lprng110+202228663 CONTROL=
     - Hh10.private
     - Ppapowell
     - J/tmp/hi
     - CA
     - Lpapowell
     - Apapowell@lprng110+202228663
     - Qt1
     - fdfA010663h10.private
     - N/tmp/hi
     - UdfA010663h10.private
     Job: papowell@lprng110+202228663 HOLDFILE=
     - active 0
     - done 0
     - hold 0
     - move 0
    ....

7.6. Job Taking Too Long - Stalled

Options used:

• stalled_time=seconds after which to report a stalled active job

The stalled_time option is actually used by the lpd server to report that a job has been active more than the indicated time with no change in state. This is useful for spotting things such a printers that are out of paper, and so forth.

7.7. Configuring Format and Displayed Information

The following sections describe options that are used by the lpd server to control how it will return status information to a lpq request.

    reverse_lpq_format=*.eng.com,130.192.0.0/16

    return_short_status=*.eng.com,130.192.0.0/16
    short_status_length#3

    force_lpq_status=s=pc*.eng.com,130.192.12.0/24,l=sun*.eng.com

8.1. lprm Queue Selection (lprm -Pprinter, lprm -a)

If no queue is specified, then the default queue is used, with -Pprinter@host causing a direct connection to the named host. The -a literal selects all queues.

8.2. lprm Job Selection

Jobs are selected by providing a job number, or glob pattern that is matched to the user name and and job identifier. If multiple patterns are provided each is applied in turn against the jobs in a queue until all have been tried. If any one of the patterns match then the job status is displayed.

If no selection information is provided then the user name performing the request is used as the selection pattern, and only the first job that matches is removed.

The all pattern will match all jobs in the queue.

The user must have permission to control the queue or to remove a selected job in order for job removal to succeed.

9.1. Informational Commands - status, flush, active, reread

The lpc status command displays the current status of various activities of interest to the system administrator. This information includes the process ID of the server and other processes.

During normal operation, when requested for job status information the lpd server will create this information and then save it in a status cache. When successive requests for the same information arrive, the cache is checked to see if the information is already in the cache and there have been no status changes. If this is the case, the cached status information is used. The lpc flush command will flush (delete) this cache information and cause the lpd server to regenerate it from the original job files.

The lpc active command connects to the print server and gets the Process ID of the lpd process. This is useful to determine if the lpd server is running on the print server.

The reread command connects to the lpd print server and requests that the server reread the printcap, lpd.conf, and lpd.perms database files.

9.2. Queue Management - enable, disable, up, down

The enable and disable commands enable and disable queuing or sending jobs to the print queue. The up command combines the enable and start commands while the down command combines the disable and stop commands.

9.3. Printing Management - start, stop, up, down

These commands are used to start and stop printing. The up combines start and enable, while down combines stop and disable.

9.4. Problem Management - abort, redo, kill

These commands are usually used when there is a problem printing a job. The abort command is used to kill off all printing activity associated with a job. It also has the side effect of stopping printing on the print queue. The redo command will redo or attempt to reprint a job. The kill command combines the abort and redo command, and is useful when there are problems with the job currently being printed and it should be reprinted.

9.5. Job Scheduling - topq, holdall, noholdall, hold, release

The topq command effectively puts the select job or jobs at the top of the queue for printing.

The holdall, noholdall, and release commands implement a simple holding queue for jobs. By default, holdall is disabled. When the holdall command enables it, then jobs will remain in the spool queue until explicitly released with the release command.

The hold command can also be used to hold individual jobs until released.

9.6. Queue Management - class, redirect, move

The class command is used to restrict printing to jobs whose class value, set using the lpr -C class option, is in the class list or matches one of the classes. This allows the administrator to restrict printing. For more details and an example of its use, see Form Support.

The redirect command allows the administrator to accepts jobs at this queue and then to have them forwarded or redirected to another print queue. This is useful when a printer temporarily is unavailable.

The move command allows an individual job (or jobs) to be forwarded or redirected to another print queue.

10.1. Maintenance

Later, you will want to use checkpc for the daily maintenance of your system. I have this line in user lp's crontab:

    32 5 * * * checkpc -t 10K -A3 -r >/dev/null 2>&1

1. truncate all log and accounting files to 10KB (-t 10K). Actually, it will keep the last 10K from the file, starting on a complete line.

2. remove all stale files older than three days (-A3 -r).

10.2. Printcap Information

You can use checkpc -V -P to examine printcaps and tell you what they contain. This is identical to the lpc server all operation, but with a higher level of verbosity.

11.1. Network Printers

The most flexible and highest throughput printer interface is via a network (TCP/IP) connection. Most high performance printers have a built in network interface, or you can attach them to a printer server box which provides a network interface. The network interface usually supports multiple network printing protocols. The most common are the LPD (RFC1179), Socket API, AppSocket, SMB, and Novell Netware interfaces. LPRng directly supports the LPD (RFC1179) and Socket API interfaces, and you can use the smbclient program from the Samba Software Package for the SMB interface.

11.2. RFC1179 (LPD) Connection

In this mode of operation the print server actually operates as a very limited BSD print spooler. These limitations include:

1. No error messages or status capability

2. Limited or very primitive banner printing. On some systems it may be impossible to turn banner printing off.

3. On most known print servers high connection activity caused by multiple systems attempting to get status or spool jobs may cause catastrophic failure of the printer.

For the above reasons, using RFC1179 to transfer jobs to a printer should be regarded as the least desirable option. Please see The RFC1189 Protocol for a detailed discussion of the RFC1179 protocol.

In order to use the RFC1179 transfer operation you must have a printcap entry for the printer that provides:

• The IP address or name of the printer that can be resolved to an IP address

• The name of the spool queue. In practice, this is usually used only to determine which of several printer ports on the print server the job will be sent to, or what type of processing the print server will do. Most cards usually do not do any processing and simply pass the job through to the printer.

The following is an example of a simple printcap entry that can be used to send a job to a remote printer using the RFC1179 protocol:

    # LPRng syntax
    # :lp value is 'where to print the job'
    lp:
      :lp=raw@10.0.0.1
    
    # OR Vintage BSD Print Spooler Syntax
    # (LPRng supports this as well)
    # :rp = remote printer, :rm = remote machine or host
    lp:
      :rp=raw:rm=10.0.0.1

If you wish to transfer jobs to a print spooler without using the full LPRng lpr program, the Perl lpr_in_perl program in the LPRng Distribution UTILS directory can be used for testing and tutorial purposes.

11.3. Socket API

The Socket API is a very flexible job transfer protocol. It is widely support by most Print Server manufacturers, with the Hewlett Packard JetDirect setting the de facto standard. The Socket API is extremely simple.

1. The user establishes a connection to TCP/IP port on the Printer or Network Print spooler. The HP JetDirect uses port 9100 by default, but other ports are used as well. This connection may be refused if the printer is busy printing a job.

2. When the network connection is established to a system which has an internal printer or for which the Network Print Spooler is an integral part of the system, the printer usually flushes all internal buffers and readies itself to receive a new job. However, when you are using an external Print Server box, you may need to send specific initialization sequences to the printer to ensure that it is reset correctly and is ready to receive new jobs.

3. When the connection is made, all bytes sent to the connection are either transferred to and external interface to directly to a print buffer used by the printer's Print Engine.

4. The connection is bidirectional, and information sent to the external port by an external printer or error messages and status generated by the printer's Print Engine will be transferred over the data link to the user.

5. The Network Print spooler will keep the connection open until it is closed by the user. During this period it may continue to report status or other information such as printer On Line, paper outages, and so forth.

6. If the connection to the printer is half-closed, that is, the shutdown() network system call is used to indicate to the remote printer that no further data will be sent, then the printer may immediately terminate the network connection. This means that no further network or status messages will be sent to the user.

7. If the connection is to a External Print Server, then usually the connection can be immediately re-established. It is the responsibility of the user to ensure that a the printer has finished its work before sending a new job.

8. If the connection is to an internal Print Server, then usually the printer will not allow the connection to be made, or will refuse all data transfers on the connection until the printer finishes with the previous job and all internal buffers have been cleared.

The following is a sample printcap showing how to use the Socket API:

    lp:
      # make a socket connection to port 9100
      :lp=10.0.0.2%9100

You can use the netcat utility by Hobbit <Hobbit@avian.org> to test that the Socket interface is available and working. If ellipse.ps is a test file, then: The simplest and easiest way to print a file to a network printer appears

      nc printer.ip.addr 9100 < file
    Example:
      nc 10.0.0.25 9100 < ellipse.ps

11.4. AppSocket TCP/IP Protocol

The AppSocket interface is supported by Tektronix and some other printer vendors. It is similar to the Socket API, with a couple of significant differences.

1. The printer has two ports for network connections: a TCP port 9100 for TCP/IP stream connections and a UDP port for UDP packet connections.

2. When a 0 length UDP packet or a UDP packet containing only CR/LF is sent to UDP port 9101, the printer will return a packet to the sender containing print status information. This information indicates the printers current status (busy, idle, printing) and any error conditions.

3. The format, reliability, and repeatability of the UDP format and information is totally undocumented, and the UPD port facility should be regarded as, at best, an advisory function of the printer.

4. To send a job to the printer, a connection to TCP port is made. This connection will be refused while the printer is busy or has a connection to another host.

5. When the TCP connection is established, the information to be printed can be sent over the TCP connection. Bytes sent on this stream will be placed in the input buffer of the Print Engine and processed.

6. An end of job (EOJ) sequence indication in the data stream will cause the printer to terminate the connection. This is different than the Socket API, where the printer will keep the connection open. This means that if the PostScript CTRL-D (end of job) character is sent in a job, then the connection will be terminated.

7. Some models of printers modify this behavior slightly and will not terminate the connection, but will simply ignore any data following the EOJ indication.

8. Some printers support bidirectional AppSocket communication, and while the connection is open will return error indications or status information.

9. Once all the data has been received and the job has finished printing, the connection will be terminated by the printer.

The ifhp filter, one of the helper programs for LPRng, is used with LPRng to provide AppSocket support. For details, please see the [IFHP-HOWTO] in the ifhp Distribution and Tektronix P450 and Family for details. The following is a typical printcap entry for the AppSocket protocol. The actual network connection to the printer is made by the ifhp filter:

    lp:
      # LPRng opens a dummy connection for consistency
      :lp=/dev/null
      # we pass the ifhp filter options indicating that the
      # Tektronics printer will need the appsocket protocol
      # and to use port 35 at 10.0.0.1 to make the connection
      # The ifhp filter may open and close the connection several
      # times during the file transfer in order to ensure that
      # the printer handles the job correctly.
      :ifhp=model=tek,appsocket,dev=10.0.0.1%35
      :filter=/usr/local/libexec/filters/ifhp

11.5. Network Print Server Boxes

A network print server is usually a box (external model) or card in a printer (internal model) which has a network connection to a TCP network and software to implement a LPD print server. If it is an external model, The parallel or serial port of the printer is connected to the box, and the print server may support multiple printers. If it is an internal model, the server is usually nothing more than a Network Interface Controller and a ROM containing software that the microprocessor in the printer uses.

The print server may support multiple printing protocols, such as RFC1179 (TCP/IP printing using the LPD print protocol), Novell Printer Protocols, SMB print protocols, and AppleTalk protocols. One of the observed problems with Network Print servers is that while they can usually support one protocol and one user at a time quite well, when you try to use multiple protocols and/or multiple users try to transfer print jobs to the printer, the printer may behave in a very odd manner. Usually this results in a printer failing to finish a job currently being printed, and unable to accept new jobs.

Several of the newer models of print servers have Simple Network Management Protocol (SNMP) agents built into them, and can provide detailed information about their internal functions. By using a SNMP manager such as SunNetmanage or HP-Openview, you can monitor your network printers activities.

I recommend that you use only a single protocol to send jobs to the printer. If you can, I also recommend that you use a print spooler and have only a single host system send a job to the printer.

My best advice on connecting to network printers is not to use the the built-in LPD server, but to use the direct TCP/IP connection to the print engine. Usually this is done to particular TCP/IP port on the printer. For the HP JetDirect and other HP products, this is usually TCP port 9100.

Once you have the direct connection, you can now use various filters to preprocess the print job, insert PJL and PCL commands, or convert text to PostScript or PCL for better print quality.

11.6. Network Print Server Configuration Information

The following is a list of print server manufacturers, models, and with hints on how to access these boxes with various protocols.

All company, brand, and product names are properties of their respective owners.

11.7. HP JetDirect Interface

The HP JetDirect Interface is one of the most widely used for network printers. For this reason it also has the most widely known set of problems. The user is strongly urged to upgrade to the latest version of firmware available for the unit. Problems with older versions of firmware include system lockups that require powerup level resets.

Newer versions of the HP JetDirect Interface have a Web Browser based configuration system. After you have assigned an IP address to the printer you can connect to the configuration port and configure the printer using the browser. If you run into configuration problems then you will most likely need to use the Microsoft Windows based JetDirect Configuration Software to reset or reconfigure the printer.

Older HPJetDirect cards can be configured only through through the front panel or through a set of network files. Here is a summary of the methods used from UNIX systems, or to use when you are desperate, to configure the printer.

     MENU  -> MIO MENU (use MENU to display MIO MENU)
     ITEM  -> CFG NETWORK=NO*
     +     -> CFG NETWORK=YES
     ENTER -> CFG NETWORK=YES*
     ITEM  -> TCP/IP=OFF* (use ITEM to display TCP/IP)
     +     -> TCP/IP=ON
     ENTER -> TCP/IP=ON*
     ITEM  -> CFG TCP/IP=NO* (use ITEM to display TCP/IP)
     +     -> CFG TCP/IP=YES
     ENTER -> CFG TCP/IP=YES*
     ITEM  -> BOOTP=NO*
         (Enable BOOTP if you want to - see below)
     ITEM  -> IP BYTE 1=0*
         This is IP address MSB byte.
         Use +- keys to change value, and then ENTER to change
         Use ITEM keys to get IP BYTE=2,3,4
     ITEM  -> SM BYTE 1=255*
          This is the subnet mask value
         Use +- keys to change value, and then ENTER to change
         Use ITEM keys to get IP BYTE=2,3,4
     ITEM  -> LG BYTE 1=255*
         This is the Syslog server (LoGger) IP address
         Use +- keys to change value, and then ENTER to change
         Use ITEM keys to get IP BYTE=2,3,4
     ITEM  -> GW BYTE 1=255*
         This is the subnet gateway (router) IP address
         Use +- keys to change value, and then ENTER to change
         Use ITEM keys to get IP BYTE=2,3,4
     ITEM  -> TIMEOUT=90
          This is the connection timeout value.  It puts a limit
         on time between connections.  A value of 10 is reasonable.

    # Example /etc/bootptab: database for bootp server (/etc/bootpd).
    # Blank lines and lines beginning with '#' are ignored.
    #
    # Legend:
    #
    #       first field -- hostname
    #                       (may be full domain name)
    #
    #       hd -- home directory
    #       bf -- bootfile
    #       cs -- cookie servers
    #       ds -- domain name servers
    #       gw -- gateways
    #       ha -- hardware address
    #       ht -- hardware type
    #       im -- impress servers
    #       ip -- host IP address
    #       lg -- log servers
    #       lp -- LPR servers
    #       ns -- IEN-116 name servers
    #       rl -- resource location protocol servers
    #       sm -- subnet mask
    #       tc -- template host (points to similar host entry)
    #       to -- time offset (seconds)
    #       ts -- time servers
    #
    # Be careful about including backslashes where they're needed.  Weird (bad)
    # things can happen when a backslash is omitted where one is intended.
    #
    peripheral1:
    :hn:ht=ether:vm=rfc1048:
    :ha=08000903212F:
    :ip=190.40.101.22:
    :sm=255.255.255.0:
    :gw=190.40.101.1:
    :lg=190.40.101.3:
    :T144="hpnp/peripheral1.cfg":

    #
    # Example HP Network Peripheral Interface configuration file
    #
    # Comments begin with '#' and end at the end of the line.
    # Blank lines are ignored.  Entries cannot span lines.
    
    # Name is the peripheral (or node) name.  It is displayed on the peripheral's
    # self-test page or configuration plot, and when sysName is obtained through
    # SNMP.  This name can be provided in the BOOTP response or can be specified
    # in the NPI configuration file to prevent the BOOTP response from overflowing
    # the packet.  The domain portion of the name is not necessary because the
    # peripheral does not perform Domain Name System (DNS) searches.  Name is
    # limited to 64 characters.
    
    name: picasso
    
    # Location describes the physical location of the peripheral.  This is the
    # value used by the interface for the MIB-II sysLocation object.  The default
    # location is undefined.  Only printable ASCII characters are allowed.
    # Maximum length is 64 characters.
    
    location: 1st floor, south wall
    
    # Contact is the name of the person who administers or services the peripheral
    # and may include how to contact this person.  It is limited to 64 characters.
    # This is the value used by the interface for the MIB-II sysContact object.
    # The default contact is undefined.  Only printable ASCII characters are
    # allowed.  Maximum length is 64 characters.
    
    contact: Phil, ext 1234
    
    # The host access list contains the list of hosts or networks of hosts
    # that are allowed to connect to the peripheral.  The format is
    # "allow: netnum [mask]", where netnum is a network number or a host IP
    # address.  Mask is an address mask of bits to apply to the network number
    # and connecting host's IP address to verify access to the peripheral.
    # The mask usually matches the network or subnet mask, but this is not
    # required.  If netnum is a host IP address, the mask 255.255.255.255 can
    # be omitted.  Up to ten access list entries are permitted.
    
    # to allow all of network 10 to access the peripheral:
    allow: 10.0.0.0  255.0.0.0
    
    # to allow a single host without specifying the mask:
    allow: 15.1.2.3
    
    # Idle timeout is the time (in seconds) after which an idle
    # print data connection is closed.  A value of zero disables
    # the timeout mechanism.  The default timeout is 90 seconds.
    
    idle-timeout: 120
    
    # A community name is a password that allows SNMP access to MIB values on
    # the network peripheral.  Community names are not highly secure; they are
    # not encrypted across the network.  The get community name determines which
    # SNMP GetRequests are responded to.  By default, the network peripheral
    # responds to all GetRequests.  The get community name is limited to 32
    # characters.
    #
    # For hpnpstat and hpnpadmin, the community name can be stored in
    # /usr/lib/hpnp/hpnpsnmp.
    
    get-community-name: blue
    
    # The set community name is similar to the get community name.  The set
    # community name determines which SNMP SetRequests are responded to.  In
    # addition, SetRequests are only honored if the sending host is on the
    # host access list.  By default, the network peripheral does not respond
    # to any SetRequests.  The set community name is limited to 32 characters.
    #
    # The set community name can come from /usr/lib/hpnp/hpnpsnmp
    # if it is the same as the get community name.  We recommend that the
    # set community name be different from the get community name though.
    
    set-community-name: yellow
    
    # SNMP traps are asynchronous notifications of some event that has occurred.
    # SNMP traps are useful only with network management software.  Traps are
    # sent to specific hosts and include a trap community name.  Up to four
    # hosts can be sent SNMP traps.   The trap community name is limited to
    # 32 characters.  The default name is public.
    
    trap-community-name: red
    
    # The SNMP trap destination list specifies systems to which SNMP
    # traps are sent.  Up to four IP addresses are allowed.  If no
    # trap destinations are listed, traps are not sent.
    
    trap-dest: 15.1.2.3
    trap-dest: 15.2.3.4
    
    # The SNMP authentication trap parameter enables or disables the sending
    # of SNMP authentication traps.  Authentication traps indicate that an SNMP
    # request was received and the community name check failed.  By default,
    # the parameter is off.
    
    authentication-trap: on
    
    # The syslog-facility parameter sets the source facility identifier that the
    # card uses when issuing syslog messages.  Other facilities, for example,
    # include the kernel (LOG_KERN), the mail system (LOG_MAIL), and the spooling
    # system (LOG_LPR).  The card only allows its syslog facility to be configured
    # to one of the local user values (LOG_LOCAL0 through LOG_LOCAL7).  The
    # selectible option strings, local0 through local7 (configured to LOG_LOCAL0
    # through LOG_LOCAL7, respectively) are case insensitive.  The default
    # syslog-facility for the card is LOG_LPR.
    
    syslog-facility: local2
    
    # This parameter allows the card to treat hosts on other subnets as if the
    # hosts were on the card's subnet.  This parameter determines the TCP
    # Maximum Segment Size (MSS) advertised by the card to hosts on other subnets
    # and affects the card's initial receive-window size.  The card will use a
    # TCP MSS of 1460 bytes for local hosts, and 536 bytes for a non-local host.
    # The default is off, that is, the card will use the maximum packet sizes
    # only on the card's configured subnet.
    #
    # The configuration utility does not allow access to this parameter.  If you
    # want to configure it, you must manually edit the NPI configuration file
    # and add it to the bottom of the entry for the network peripheral.
    
    subnets-local: on
    
    # This parameter affects how the card handles TCP connection requests from
    # the host.  By default, the JetDirect MPS card will accept a TCP connection
    # even if the peripheral is off-line.  If this parameter is set to "on", then
    # the card will only accept a TCP connection when the peripheral is on-line.
    
    old-idle-mode: off

11.8. Printing to a SMB (MicroSoft) Printer

Microsoft use the SMB (Simple Message Block) protocol to transfer files and print jobs to hosts and printers. SMB can be used over TCP/IP, NetBEUI, IPX, and other lower level network protocols.

Unfortunately, most printers do not provide detailed status or error reports when using the SMB protocol. There are a very large number of printers that have deficient SMB support that causes problems when used in a high traffic or high throughput environment.

It is highly recommended that this protocol not be used unless there is no alternative.

If you have a printer or a remote print spooler that supports SMB You can use the SAMBA smbclient program to send a print job to an SMB client. The following is a sample Shell Script script which you can use:

    #!/bin/sh -x
    # This script is an input filter for printcap printing on a unix machine. It
    # uses the smbclient program to print the file to the specified smb-based
    # server and service.
    # The 'smb' printcap entry below shows how to configure LPRng
    # for printing
    #
    # smb:
    #  :lp=|/usr/local/samba/smbprint
    #  :sd=/var/spool/smb:
    #  :filter= ... filter ...
    #
    # The /var/spool/smb/.config file should contain:
    #   server="PC_SERVER"
    #   service="PR_SHARENAME"
    #   password="PASSWORD"
    #
    # Set PC_SERVER to the server, PR_SHARENAME to the printer,
    # and PASSWORD to the password for this service.
    #
    # E.g.
    #   server=PAULS_PC
    #   service=CJET_371
    #   password=""
    #
    #
    config_file=.config
    if [ -f $config_file ] ; then
        eval `/bin/cat $config_file`
    fi
    #
    # NOTE You may wish to add the line `echo translate' if you want automatic
    # CR/LF translation when printing.
    (
    #   echo translate
        echo "print -"
        /bin/cat
    ) | /usr/local/bin/smbclient "\\\\$server\\$service" \
       "$password" -U "$server" -N -P 1>&2

If the above script was in /usr/local/libexec/filters/smbprint, the printcap entry for this printer would be:

    pauls_pc:
      :sd=/var/spool/lpd/%P
      # we filter the output
      :lp=|/usr/local/libexec/filters/smbprint
      # you can add filters if you want to do specific actions
      :ifhp=model=hp4
      :filter=/usr/local/libexec/filters/ifhp

11.9. Printing to AppleTalk Printers

The netatalk package comes with the pap program that can be used to transfer jobs using the AppleTalk protocol. A printcap entry for a network printer looks like the following:

    atalk:
      :lp=| -$ /usr/local/atalk/bin/pap -e -p "npbname"
      :sd=/var/spool/lpd/atalk
      :ifhp=model=ps,status@
      :filter=/usr/local/libexec/filters/ifhp

The -$ suppress the addition of extra parameters to the pap command line. The pap program must be SETUID root and executable only by root or group daemon. This can be done by using the following script:

    h4: {309} cd /usr/local/atalk/bin
    h4: {310} chown root pap
    h4: {311} chgrp daemon pap
    h4: {312} chmod 550 pap
    h4: {313} chmod s+u pap

11.10. Parallel Port Printers

When installing a parallel port printer, there are three elements of concern: the physical hardware connection (cable and connectors), the IO device and Operating System support, and finally the print spooler support for the device.

Originally most parallel port devices were strictly write only with a minimum amount of error information - only hardware signals for online, out of paper and fault were present. Due to the lack of any other way to interface devices to the Intel based PC platform, desperate hardware designers in search of a cheap (free?) way to interface their IO devices developed ways to manipulate the signals and do bidirectional communication. Needless to say, no two companies developed the same methods, and no two companies were compatible with any other companies method.

In 1994, the IEEE 1284 standard was first developed,. The following information is courtesy of Warp Nine Engineering, of San Diego, CA, from the http://www.fapo.com/1284int.htm web page.

When IBM introduced the PC, in 1981, the parallel printer port was included as an alternative to the slower serial port as a means for driving the latest high performance dot matrix printers. The parallel port had the capability to transfer 8 bits of data at time whereas the serial port transmitted one bit at a time. When the PC was introduced, dot matrix printers were the main peripheral that used the parallel port. As technology progressed and the need for greater external connectivity increased, the parallel port became the means by which you could connect higher performance peripherals. These peripherals now range from printer sharing devices, portable disk drives and tape backup to local area network adapters and CD ROM players.

The problems faced by developers and customers of these peripherals fall into three categories. First, although the performance of the PC has increased dramatically, there has been virtually no change in the parallel port performance or architecture. The maximum data transfer rate achievable with this architecture is around 150 kilobytes per second and is extremely software intensive. Second, there is no standard for the electrical interface. This causes many problems when attempting to guarantee operation across various platforms. Finally, the lack of design standards forced a distance limitation of only 6 feet for external cables.

In 1991 there was a meeting of printer manufacturers to start discussions on developing a new standard for the intelligent control of printers over a network. These manufacturers, which included Lexmark, IBM, Texas Instruments and others, formed the Network Printing Alliance. The NPA defined a set of parameters that, when implemented in the printer and host, will allow for the complete control of printer applications and jobs. While this work was in progress it became apparent that to fully implement this standard would require a high performance bi-directional connection to the PC. The usual means of connection, the ordinary PC parallel port, did not have the capabilities required to meet the full requirements or abilities of this standard.

The NPA submitted a proposal to the IEEE for the creation of a committee to develop a new standard for a high speed bi-directional parallel port for the PC. It was a requirement that this new standard would remain fully compatible with the original parallel port software and peripherals, but would increase the data rate capability to greater than 1M bytes per second, both in and out of the computer. This committee became the IEEE 1284 committee. The IEEE 1284 standard, "Standard Signaling Method for a Bi-directional Parallel Peripheral Interface for Personal Computers", was approved for final release in March of 1994.

Even if your hardware has support for the IEEE 1284 high speed bidirectional data transfers, your Operating System drivers must support it. Unfortunately, there is no universal agreement on the capabilities that should be provided by the low level printer port device drivers, and the method for supporting them. A good example of the problem of OS support and drivers is given by the Linux Parallel Port group, currently headed by Tim Waugh, and which is documented in the http://people.redhat.com/twaugh/parport/ and http://people.redhat.com/twaugh/parport/html/parportguide.html web pages.

Given this state of affairs, it should be no surprise that there is no support for bidirectional parallel port printers in LPRng. In fact, it turns out that there are severe problems with many Unix implementations that cause extreme headaches. These include:

• While a parallel port may be opened Read/Write, a read() will either block indefinitely or cause a major system failure (crash).

• There is no buffering of data in the low level driver; that is, once a write() starts, then the process will block until the data is written out. If the write() call is interrupted by a signal and not immediately restarted, then the status returned by the write() may be an error indication (-1) or the numbers of bytes that were actually written. If an error is returned, then an unknown number were written and the print job must be aborted.

• Many Operating systems do not implement a select() functionality for the parallel port, which means that it is difficult to do a multi-threaded implementation. Instead, a polling method must be used.

The good news is that on all known systems, if the parallel port device is opened exclusively for writing, and a blocking write() is used, and the write() is not interrupted, and there are no device errors, then data is delivered correctly to the device.

In most UNIX systems the printer port has the name /dev/lpt, /dev/prn, or something similar. On most systems the dmesg utility will print a list of IO devices found during system configuration. Use the following commands to get the information and scan for the device. You should also make sure that the printer device is available.

    dmesg >/tmp/a
    grep lp /tmp/a
    ls /dev/lp*

Gordon Haverland <haverlan@agric.gov.ab.ca> supplied this little script, that will assist with this:

    #!/bin/sh
    #set -v -x              # uncomment for debugging
    PATH=/bin:/usr/bin
    printer=
    for printer in /dev/lp* ;
    do
        echo PRINTER TEST to $printer 1>&2
        for i in 1 2 3 4 5 6 7 8 9;
        do
            echo PRINTER $printer $i > $printer;
        done
        echo -e \\r\\f > $printer
    done
    exit 0;

If your printer is connected to the device name you provided, then you should get a page of something out. If the output suffers from the staircase effect, you will see the numbers marching across the page, otherwise the numbers will all be in a single column.

11.11. Serial Printers

If your printer is attached by a serial line, then you may need to set the serial line characteristics before sending the job to the printer. Here are a set of guidelines to following when attaching a serial port printer to a serial line.

1. Check to make sure that the line is not enabled for login. Logins are usually managed by the getty (BSD) or ttymon (Solaris, SystemV). Check your system documentation and make sure that these daemons are not managing the serial line.

2. Check the permissions and ownership of the serial line. For the most easy testing, set the permissions to 0666 (everybody can open for reading and writing). After you have made sure that you can send jobs to the printer, you might want to change the ownership of the serial line to the lpd server and change the permissions to 0600.

3. Make sure that you can print a test file on the printer via the serial port. This may require setting the line characteristics and then sending a file to the printer. You should try to use 8 bit, no parity, with hardware flow control and no special character interpretation, and definitely no LF to CR/LF translation. The problem is that different versions of UNIX systems have different sets of stty(1) commands to do this. The following simple test script can help in this.

    #!/bin/sh
    # 9600, no echo, no CR
    FLAGS= 9600 -raw -parenb cs8 crtscts
    DEV= /dev/tty01
    (stty $FLAGS; stty 1>&2; cat $1 ) <$DEV >$DEV

This shows using stty to set the flags, then to print the current settings, and then using cat a file to the output. If you attach a dumb terminal to the serial port, you can even use this script to ensure that input from the device is echoed to the output with the correct speed, parity, etc.

Experience has shown that serially connected printers are the least reliable and lowest speed. Where possible, it is strongly recommended that they be attached to a network print box which will provide a Socket API interface and handle the low level network to serial port protocol conversions.

12.1. The Printcap Parsing Rules

Options used:

• client FLAG printcap entry valid only for client programs

• oh= hosts where printcap entry valid

• server printcap entry valid only for lpd server

• tc add named printcap entry contents

In this section, we will discuss the remaining tricky parts of the LPRng printcap database: combined client and server printcaps, host specific printcap entries, and the tc include facility.

The following is a complete description of how a printcap file is processed:

1. When processing a printcap file, the LPRng software reads and parses each entry individually. Leading whitespace is removed. Lines starting with # and blank lines are ignored.

2. Lines ending with \ will have the \ discarded, and all lines of a printcap entry are joined by removing the line separators (\n) and replacing them with a space.

3. The printcap entry is parsed, and the printcap name, aliases, and options are determined. Colons : act as option separators, and leading and trailing whitespaces are removed.

4. Options are sorted and except for the tc=... option only the last option setting is retained.

5. If an option value requires a colon, then the \: or \072, the same escaped character value as used in the C, Perl, tcl, and other programming languages, can be used.

6. Client programs will discard a printcap entry with a server option and server programs will discard a printcap entry with a client options.

7. The oh (on this host) option specifies a list of IP addresses and mask pairs or glob strings which are used to determine if this printcap entry is valid for this host (see discussion below).

8. After the above processing, if there is an existing termcap entry with the same name, the two sets of options are combined, with the last option setting retained except for the tc entries which are combined.

9. When a printcap entry is actually used, the printcap entries listed by the tc include option are extracted and combined in order. This allows include entries to appear after the referring printcap entry. Then printcap options will be combined with the included ones. This has the effect that the options specified in the printcap entry will override the ones from the tc included entries.

10. Finally, each string printcap option with a %X value has %X replaced by the following values. Unspecified values will not be modified.

    Key	Value	Purpose
    %P	printcap entry primary name
    %Q	queue requested
    %h	short host name (host)
    %H	fully qualified host name (host.dns.whatever)
    %R	remote printer (rp value)
    %M	remote host (rm value)
    %D	date in YYYY-MM-DD format

    
    
    

11. When parsing multiple printcap files, these are processed in order, and all of their printcap entries are combined according to the above procedures. The tc resolution and %X expansion is done after all the files have been processed.

The following examples show how to use the above rules to your advantage. You can combine both client and server printcap information in a single file as well as dividing a printcap entry into several parts. Here is an example:

    # seen by both client and server
    lp1:lp=lp@pr1:mx=100
    lp1:sd=/usr/local/spool/lp1:mx=0
    # seen only by client
    lp2:lp=lp@pr2:client
    # seen only by server
    lp2:lp=/dev/lp:server

1. Printcap entries with the same name are combined. The first printcap entry, lp1, the information is seen by both client and server. The next printcap entry, with the same name lp1, will be combined with the first one. The order of options is important - the entries are scanned in order and an option will have the last value set. Thus, after having read both the lp1 printcap entries, both client and server will have:

       lp1:lp=lp@pr1
         :mx=0
         :sd=/usr/local/spool/lp1
   

   
   
   

2. The lp2 has a client and server version. This is recommended when complex printcaps on multiple hosts and servers are used. Thus, the LPRng clients will see:

       lp1
         :lp=lp@pr1
         :mx=0
         :sd=/usr/local/spool/lp1
       lp2
         :client
         :lp=lp@pr2
   

   and the server will see:

       lp1
         :lp=lp@pr1
         :mx=0
         :sd=/usr/local/spool/lp1
       lp2
         :lp=/dev/lp
         :server
   

   
   
   

If you have multiple printers of the same type whose configuration is almost identical, then you can define a set of tc only printcap entries containing common information and use the tc include facility.

Printcap entry names may start with period (.), question mark (?), or exclamation mark (!), followed by one or more alphanumeric , underscore (_) or hyphen (-) characters. Queue or printer names start with an alphanumeric character. Printcap entries whose names do not start with an alphanumeric character can only be used as targets of the tc include facility. For example:

    .hp:
      :sd=/usr/local/spool/%P
      :mx=0
    hp1:tc=.hp,.filter
      :lp=lp@10.0.0.1
    hp2:tc=.hp,.filter
      :lp=lp@10.0.0.2
    .filter
      :filter=/usr/local/libexec/filters/ifhp

1. The .hp and .filter printcap entities are not spool queue definitions. After tc include processing is completed, the printcap information would resemble:

       hp1
         :lp=lp@10.0.0.1
         :filter=/usr/local/libexec/filters/ifhp
         :mx=0
         :sd=/usr/local/spool/%P
       hp2
         :lp=lp@10.0.0.2
         :filter=/usr/local/libexec/filters/ifhp
         :mx=0
         :sd=/usr/local/spool/%P
   

   
   
   

2. The %X processing will replace %P with the printcap name, so we would have:

       hp1
         :lp=lp@10.0.0.1
         :filter=/usr/local/libexec/filters/ifhp
         :mx=0
         :sd=/usr/local/spool/hp1
       hp2
         :lp=lp@10.0.0.2
         :filter=/usr/local/libexec/filters/ifhp
         :mx=0
         :sd=/usr/local/spool/hp2
   

   
   
   

12.2. Simple Client Printcap Entry

Options used:

• client FLAG client printcap entry

• lp=destination printer information

• rm=remote host (machine)

• rp=remote printer

I'll use this simple example to explain the basics of the LPRng printcap format and introduce some of the LPRng network configuration options. Here is a simple printcap file used to provide client programs (lpr, lprm, etc) with remote printer and server information.

    # printer lp1
    lp1|printer1
      :rm=localhost
    # printer lp2 with continuation
    lp2:\
      :lp=pr@10.0.0.1:client
    # printcap lp3, to printer pr, with overrides
    lp3:rp=pr:rm=hp.private
      :force_localhost@
    # Simplest possible printcap entry - defaults for everything
    lp4

1. Lines starting with a # sign are comments, and all leading and trailing whitespace, i.e. - spaces, tabs, etc, are ignored. Empty lines are ignored as well.

2. A printcap entry starts with the printcap entry name, followed by one or more aliases, followed by one or more options. In the above example we have three printcap entries: lp1 with an alias printer1 and lp2, lp3, and lp4 with no aliases.

3. Aliases start with the | character and options with the : character; tabs and spaces before and after the | or : characters and at the start and end of lines are ignored. You can use backslash (\) at the end of a line to create a multi-line value for an option. The backslash will cause the next line to be appended to the current line; watch out for comments and ends of printcap entries if you use this facility. As you can see from the example, there is no Name printcap entry - this is part of the cm option on the previous line.

4. Options take the form of a keyword/value pair, i.e.-

   :option=value
   :option#value   (legacy, not advised for new systems)
   :option
   :option@

   
   
   

5. Option names are case insensitive, but option values are not. While Ts and ts are the same option name, ts=Testing and ts=testing have their case preserved. A string or integer value is specified by option=value or option#value.

6. The use of the legacy option#value form is NOT recommended as some preprocessors and database systems will treat # as the start of a comment and delete the remainder of the line. This has caused great consternation for sysadmins who wonder why their NIS distributed printcap entries have been mysteriously truncated.

7. If you want to set a string option to empty value, use option=. The option will set it to 1. If an option value contains a colon, then use the C (or Perl or Tck/Tk) string escape \072 to represent the value.

8. Boolean options are set TRUE (1) if no value follows the keyword and FALSE (0) by appending a @. For example sh will set sh to TRUE and sh@ to FALSE.

There may be multiple options on the same line, separated by colons.

Now let's examine the first printcap entry in detail. It is reproduced here for convenience:

    # printer lp1
    lp1|printer1
      :rm=localhost

1. We start with a comment, followed by the printcap entry name and and alias. Aliases are useful when you want to refer to a single printer or print queue by different names. This can be useful in advanced printcap and print queue setups. By default, the remote printer name is the printcap entry name.

2. The rm (remote machine or host) option specifies the name or IP address of the lpd host running lpd. In this example the remote host is localhost or the machine that the client is running on and we assume that the lpd server is running on the localhost. Thus, we would communicate with printer lp1@localhost.

Let's look at the next printcap entry:

    # printer lp2 with continuation
    lp2:\
      :lp=pr@10.0.0.1:client

1. The lp2 printcap entry illustrates the use (and abuse) of the \ continuation. If you think about this, we have really defined a printcap entry of the form:

       lp2: :lp=pr@10.0.0.1:client
   

   
   
   

   Luckily, LPRng ignores empty options like ::. While it is strongly recommended that \ be avoided it may be necessary for compatibility with other system utilities.

2. The lp=pr@10.0.0.1 literal is an alternate way to specify a remote queue and server. If the force_localhost default is being used, then the LPRng clients will ignore the 10.0.0.1 address and still connect to pr@localhost. There is further discussion about this in the next section.

3. The client option explicitly labels client only printcap information. The lpd server will ignore any printcap with the client option. When constructing complex printcaps, this option is used to keep ensure that you have consistent printcap information.

    lp3:rp=pr:rm=hp.private
      :force_localhost@

1. The rp= (remote printer) remote print queue name to used when sending commands to the lpd print server.

2. The force_localhost@ literal is an example of a flag option. The @ sets the literal value to 0 (false). We set force_localhost to false, which now allows the LPRng clients to connect directly to the specified remote printer. In this example, the hp.private could be a HP LaserJet Printer with a JetDirect interface, which supports the RFC1179 protocol.

3. One disadvantages of sending a job directly to a printer using the above method is that lpr program will not terminate or exit until all of the files have been transferred to the printer, and this may take a long time as the printer processes the files as they are received.

Now let's look at the last printcap entry:

    # Simplest possible printcap entry - defaults for everything
    lp4

The last example is the simplest possible printcap entry. This will cause LPRng clients to use the default values for everything. The printer will be lp4, i.e. - the name of the printcap, and the server will be localhost if force_localhost is set, or the value of the default_remote_host configuration option if it is not.

12.3. Simple Server Printcap Example

Options used:

• cm=comment for status

• filter=job filter

• lf=log file

• af=accounting file

• lp=output device

• mx=maximum job size

• sd=spool directory file

The previous section discussed printcap entries for use by the client programs. Now we will discuss printcap entries for use by the lpd server. In simple configurations or when we have the force_localhost option enabled we can use the same printcap for both LPRng clients and the lpd server.

    # Local ASCII printer
    lp1|printer
      :server
      :cm=Dumb printer
      :lp=/dev/lp1
      :sd=/var/spool/lpd/lp1
      :lf=log:af=acct
      :filter=/usr/local/libexec/filters/ifhp
      :mx=0

1. The printcap entry name is lp1. This information will be displayed when requesting status information using the lpq program.

2. The printer alias. This allows a single spool queue to have multiple names.

3. The :server option specifies this printcap entry is only used by lpd server.

4. The :cm field supplies a information field for lpq (printer status) output.

5. The :lp value specifies the destination file, device or remote spool queue to which data is sent. In this example it is the device /dev/lp1. By default, IO devices are opened for write-only operation.

6. The :sd=/path specifies the spool directory where print job files are stored until they are printed.

7. The :lf and :af options specify the names of the log and accounting files, respectively. These have the default values log and acct respectively. If not an absolute path, the file is relative to the spool queue directory. If these files don't exist, they will not be created, and no logging or accounting will be done. You will need to create them manually (e.g., by using touch) or by using the checkpc program. If you do not want a log or accounting file, then use :lf=, i.e. - no value.

8. The :filter=/path option specifies a filter program to be used to process job files. Filters and print formats are discussed in Filters.

9. mx indicates the maximum file size for a print job. Specifying 0 means that there is no limit.

12.4. Using :oh To Select Printcap Information

When administering a large number of printers over a large area, it is sometimes desirable to have a default printer for each host. This default printer may be different for each host, and can be selected by using the oh entry. The oh value is a list of the following entries

    [!] IP/n     - address + mask length    10.0.0.0/8
    [!] IP/IP    - address + mask           10.0.0.0/255.0.0.0
    [!] vvv      - glob for hostname        pc*.org.com

The LPRng software will determine the hostnames and IP addresses assigned to the host and then check to see if there is a match in the listed hostnames or IP addresses. The optional test inversion (!) causes the sense of the match to be inverted. The list of addresses or entries are tested in sequence until a match is found. If no match is found the printcap entry will not be used. For example:

    lp:oh=*.admin.org.com,10.0.0.5,10.2.0.0/16:lp=pr1@server1
    lp:oh=*.eng.org.com:lp=hp@server2
    color:oh=*.eng.org.com:lp=color@server3
    color:oh=!*.eng.org.com:lp=color@server4

In the above example, if our host name is booster.admin.org.com, then we would use lp=pr1@server1, as the *.admin.org.com glob pattern would match our host name.

if our host name is booster.dev.org.com and our IP address is 10.2.0.1, then we would use lp=pr1@server1, as the 10.2.0.0/16 ip address would be in the specified address range.

Finally we have an example of the use of the match inversion operator (!). All hosts whose name matches *.eng.org.com will use color@server3 and the others will use color@server4.

12.5. Using the Wildcard Printcap Entry

The wildcard printcap name * is used to select a default or printcap entry when a match is not found in the printcap database.

    # %P and %Q set to printer name
    *:lp=%P@server
    
    # %P set to 'printer', %Q set to printer name
    printer|*:lp=%P@server

When searching for printcap information, the LPRng software will first search for an exact match for a printcap entry against the printcap names and aliases. If non is found, it then searches for a wildcard entry and uses the first one found with a wildcard name or alias.

If the wildcard * is the printcap name, then the printer name (%P value) and queue (%Q value) are set to the name being searched for. If the wildcard is an alias, then then printer name is set to the printcap main entry name and the queue to the name being searched for.

12.6. Enterprise Strength Printcap Example

Most system administrators want to have a single printcap file that can be distributed or referenced from all the hosts under their administrative control. The following show how several large institutions have organized their printcap information. It uses the following principles:

• Many times it is necessary to partition groups of users into areas that have particular printing setups, but use the same queue name for different printers. This is done by using the :oh (on this host) option to select the printcap to be used.

• Provide as little information as possible to the systems that do not have print spoolers. This is because they will simply forward their requests to a print spooler and it is not necessary to have the information for a printer. As we will see in an example below, this can be very simple to do.

• Provide a default printer so that when the user does not have a printer explicitly selected then he will get well behaved results.

• For each family of printers, develop a standard method of interfacing to them. This means that the filter, options, and other things should be identical.

• For each server, provide a uniform set of standards for the spool queues for a printer. If the spool queue is simply used to store and forward jobs, then provide a standard default operation for this queue. If the spool queue directly feeds a printer, use the default options for the printer, and then refine them with printer specific information.

    # client setups; note brutality of this method that
    #  assigns servers to clients based on their names
    #  you could do this for IP addresses as well
    # lp1 is default printer for Engineering
    #   Default client information
    .client=force_localhost@
    #
    lp1:oh=*.eng.com:lp=%P@server1.eng.com:tc=.client
    *:oh=*.eng.com:lp=%P@server1.eng.com:tc=.client
    color:oh-*.admin.com:lp=%P@server2.admin.com:tc=.client
    *:oh=*.admin.com:lp=%P@server2.admin.com:tc=.client
    lowres:lp=%P@general.services.com:tc=.client
    *:lp=%P@general.services.com:tc=.client
    
    # Standard Printer Configurations
    # this is for the HP4simx, we use a standard filter setup
    .cf_hp4simx
     :ifhp=model=hp4simx
     :filter=/usr/local/libexec/filters/ifhp
    .cf_hplj5000
     :ifhp=model=hp5000
     :filter=/usr/local/libexec/filters/ifhp
    # now we define the printers that use them
    .pr_eng1:cm=Engineering's Printer 1
     :tc=.cf_hplj5000:lp=10.0.0.2%9100
    .pr_eng2:cm=Engineering's Printer 2
     :tc=.cf_hplj5000:lp=10.0.0.23%9100
    
    # now we define the server entries
    # We set up server entries and then forward
    #  to a single server that sends the the printer
    
    .server
     :sd=/var/spool/lpd/%P
     :mx=0
    pr1:oh=!10.0.0.5:lp=%P@10.0.0.5:server:tc=.server
    pr1:oh=10.0.0.5:tc=.server
     :tc=.pr_eng1

12.7. Remote Printer Using RFC1179

Options used:

• lp=destination

• rm=remote host (machine)

• rp=remote printer (machine)

You can have the lpd server forward jobs to another server or print which supports the RFC1179 protocol by using the following printcap:

    # Simplest
    remote|Remote Printer
       :lp=raw@server
    # historical
    remote:
      rp=raw:rm=server
    # Sometimes you have to connect to a non-standard port
    special:lp=lp@server%2000

1. If the lp printer entry is present, it will override the rm and rp printer entries.

2. The lp=pr@host format specifies that the output device is actually a remote spool queue, and jobs should be transferred using RFC1179 protocol.

3. By default, LPRng will attempt to sanitize all jobs that it originates or forwards. This sanitization will result in an RFC1179 compliant control file, and will not modify any of the job information.

12.8. Remote Printer Using Socket API

If the spool queue destination is a remote printer supporting the Socket API, then you can have LPRng open a connection directly to the printer. These include the older Apple printers with TCP/IP support and the HP JetDirect supported printers.

    # Simplest
    remote
       :lp=10.24.2.3%9100

1. The lp=server%port or lp=IPaddr%port format specifies that lpd should open a TCP/IP connection to the remote host and simply transfer verbatum the files to be printed.

2. The sh and sf will prevent lpd from trying to generate banner pages or put form feeds between jobs.

While this is the simplest printcap, it is also the most dangerous as there is nothing to prevent a malformed job from being sent to the printer. The next printcap example is much more robust:

    # Simplest
    remote
       :lp=10.24.2.3%9100
       :of=/usr/local/libexec/filters/ifhp
       :filter=/usr/local/libexec/filters/ifhp

1. This version will use the ifhp filter to precondition the printer and to process jobs. See ifhp Filter for details. The ifhp filter will perform the appropriate printer resets, translate job information, and ensure correct printer operation in the presence of errors. It will also produce voluminous error messages and status information.

12.9. Parallel Printer

The parallel printer printcap is very simple.

    # parallel printer
    lp:
       :lp=/dev/lpr

1. The lp=/dev/lpr specifies that lpd should open the device for APPEND and simply transfer job files to it.

2. The sh and sf will prevent lpd from trying to generate banner pages or put form feeds between jobs.

If you discover that UNIX print jobs result in a staircase appearance, then you need to force your printer to do LF (linefeed) to CR/LF (carriage return/line feed) translation, or do the translation yourself.

    # Simple parallel printer
    lp:
       :lp=/dev/lpr
       :filter=/usr/local/bin/lpf

By using the if=...lpf filter, the job will be passed through the lpf filter, which will do the LF to CR/LF translation.

If you have a more complex printer that handles PostScript, PCL, and PJL, then you will need to use the more powerful ifhp filter:

    # Simple parallel printer
    lp:
       :lp=/dev/lpr
       :ifhp=model=hp4,status@
       :of=/usr/local/libexec/filters/ifhp
       :filter=/usr/local/libexec/filters/ifhp

See ifhp Filter for details. This entry will specify that the printer is an HP4, and that no status information is available. This is usually the case with a parallel port.

12.10. Serial Printer

Options used:

• br=serial port bit rate

• rw FLAG device opened RW

• stty=stty options for serial port configuration

The following is a typical printcap for a serial printer: