824 lines
22 KiB
Text
824 lines
22 KiB
Text
.HTML "A Guide to the Lp Printer Spooler
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.TL
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A Guide to the Lp
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Printer Spooler
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.AU
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Paul Glick
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pg@plan9.bell-labs.com
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.AB
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.PP
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.I Lp
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is a collection of programs used to provide an easy-to-use
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interface for printing a variety of document types on a variety
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of printers.
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.I Lp
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is the glue that connects various document language
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translators and printer communication programs together so that
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the users may have a consistent view of printers.
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Most of the glue
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is shell script, which can be easily modified.
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The user need not
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specify options to get sensible output in most cases.
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.I Lp
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is described here
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so that others may make additions and changes.
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.AE
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\" .2C
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.NH
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Introduction
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.PP
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.I Lp
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is used to format and print data on a variety of output devices.
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The need for
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.I lp
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was rooted in the inability of other printer spoolers to do simple
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tasks without a great deal of user specification of options.
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At the time
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.I lp
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was written, there were several printer
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languages, such as ImPress and PostScript, and
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an internally developed printer that would accept
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.I troff
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output.
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Now, all our printers take PostScript,
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but printers that use HPCL and HPGL abound and
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support for those printers may be added easily.
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A great deal of what underlies
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.I lp
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is taken from BSD's
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.I lpr
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and System V's
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.I lp .
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The important features of this system are that most of the programs
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are easily modified shell scripts and the user need not
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learn to use the large amount of underlying software developed by others.
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.I Lp
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runs under Plan 9 and several flavors of
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UNIX.
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This document deals with
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.I lp
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as it relates to Plan 9.
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.I Lp
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was developed using both Datakit and Ethernet to transport data between machines.
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Now only the Ethernet transport mechanism remains.
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.PP
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Text, graphics, and formatted text files are appropriately processed and
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placed into a spool directory from which they are taken to be printed by a daemon process.
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Additional functions include checking the status of a printer queue
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and removing jobs from the printer queue.
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.PP
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All the shell scripts (see
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.I rc (1))
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associated with
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.I lp
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reside in the spool directory
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.CW /sys/lib/lp
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except for the
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.I lp
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command itself, which resides in
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.CW /rc/bin .
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Commands related to
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.I lp
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that are not shell scripts can most often be found
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in
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.CW /$cputype/bin/aux .
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The directory where all the
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.I lp
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scripts reside is defined within
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.I lp
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by the shell variable
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.CW LPLIB .
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In the remainder of this document, file names will be specified
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with this shell variable as their root.
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.NH
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Usage
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.PP
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.I Lp
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requires an output device to be specified
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before it will process input.
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This can be done in any of three ways described here.
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.IP 1)
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The file
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.CW $LPLIB/defdevice
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may contain the name of a default output device.
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This may not be practical for environments where
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there are many printers.
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.IP 2)
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The user's environment variable
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.CW LPDEST
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may be set to the name of the device to be used.
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This is often a more practical solution when there are several printers
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available.
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This overrides a
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.CW defdevice
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specification.
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.IP 3)
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The
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.CW -d
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.I printer
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option to the
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.I lp
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command specifies
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.I printer
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as the device to which output should be directed, overriding the
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previous two specifications.
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.PP
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.ti 0
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If
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.I printer
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is
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.CW ? ,
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a list of printers and other information in the
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.CW devices
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file is printed, as shown in Figure 1.
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Quote the question mark to prevent it from being
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interpreted by the shell language as a metacharacter.
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\" .1C
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.KF
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.P1
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% lp -d'?'
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device location host class
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fn 2C-501 helix post/2+600dpi+duplex
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pcclone - - post+nohead
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peacock 2C-501 cetus post/2+300dpi+nohead+color
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ps83 st8_fl3 rice post+300dpi+reverse
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psu 2C-501 cetus post/2+1200dpi
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.
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.
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.
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%
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.P2
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.ce
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.I "Figure 1. Sample listing of installed printers"
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.KE
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.PP
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Normally,
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.I lp
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uses the
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.CW file
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command to figure out what type of input it is receiving.
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This is done within the
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.CW generic
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process which is discussed later in this paper in the
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.B "Process directory"
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section.
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To select a specific input processor the
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\f(CW-p\fP\fIprocess\fP
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option is used where
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.I process
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is one of the shell scripts in the
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.CW process
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directory.
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.LP
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Troff
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output can be printed, in this case, on printer
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.I fn
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with
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.P1
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% troff -ms lp.ms | lp -dfn
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.P2
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.LP
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A file can be converted to PostScript using the pseudo-printer
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.CW stdout :
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.P1
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% troff -ms lp.ms | lp -dstdout > lp.ps
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.P2
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LaTeX (and analogously TeX)
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documents are printed in two steps:
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.P1
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% latex lp.tex
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.
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.
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% lp lp.dvi
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.
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.
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%
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.P2
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LaTeX
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produces a `.dvi' file and
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does not permit the use of a pipe
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connection to the standard input of
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.I lp .
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To look at the status and queue of a device, use
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.CW -q :
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.P1
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% lp -dpsu -q
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daemon status:
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: 67.17% sent
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printer status:
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%%[ status: busy; source: lpd ]%%
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queue on cetus:
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job user try size
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rice29436.1 pg 0 17454
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slocum17565.1 ches 1 49995
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%
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.P2
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This command can print the status and queue of the local
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and remote hosts.
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Administrators should be advised that working in an environment where the
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.I lp
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spool directory is shared among the local and remote hosts,
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no spooling should be done on the local hosts.
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The format of the status and queue printout is up to the administrator.
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The job started above can be killed with
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.CW -k :
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.P1
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$ lp -dpsu -k rice29436.1
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rice29436.1 removed from psu queue on cetus
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.P2
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.NH
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Options
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.PP
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There are options available to modify the way in which a job is handled.
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It is the job of the
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.I lp
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programs to convert the option settings so they may be used by each of the
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different translation and interface programs.
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Not all options are applicable to all printer environments.
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Table 1 lists the standard
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.I lp
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options, the shell variable settings, and description of the options.
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\" .1C
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.KF
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.sp
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.in 0
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.TS
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center;
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c | c s s | c
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c | c c c | c
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lfCWp-2 | lfCWp-2 cfCWp-2 cfCWp-2 | lp-2w(3i).
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=
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option shell variable action
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\^ name default set \^
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_
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-D DEBUG N 1 turn on debugging mode.
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_
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-H NOHEADER N 1 suppress header page.
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_
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-L LAND N 1 make long page dimension horizontal.
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_
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-M \fImach\fP LPMACHID N \fImach\fP set the source machine name.
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_
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-Q QONLY N 1 do not execute daemon; for debugging.
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_
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-c \fIn\fP COPIES N \fIn\fP number of copies to be printed.
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_
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-d \fIprinter\fP LPDEST U \fIprinter\fP set job destination; override other settings.
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_
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-f \fIfont.pt\fP FONT N \fIfont\fP set font style and point size for printing.
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POINT N \fIpt\fP
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_
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-i \fIn\fP IBIN N \fIn\fP T{
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select input paper tray options.
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The argument given is dependent on the printer type.
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A number can be given to select a particular tray and/or
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.CW simplex
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or
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.CW duplex
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may be used to get single or double sided output, where
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applicable.
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Multiple options should be separated by commas.
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T}
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_
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-k KILLFLAG 0 1 T{
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take non-option arguments as job numbers to be removed from queue.
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T}
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_
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-l \fIn\fP LINES N \fIn\fP T{
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for printed data, the number of lines per logical page.
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T}
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_
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-m \fIf\fP MAG N \fIf\fP T{
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magnify the image by a factor \fIf\fP.
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The factor should be a positive real number.
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T}
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_
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-n \fIn\fP NPAG N \fIn\fP T{
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put \fIn\fP logical pages on a single physical page.
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A simple algorithm is used to pack the pages.
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T}
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_
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-o \fIlist\fP OLIST N \fIlist\fP T{
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print only those pages specified in the list.
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The list may be a sequence of numbers or ranges separated by commas.
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A range is a pair of numbers separated by a hyphen.
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T}
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_
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-p \fIproc\fP LPPROC L \fIproc\fP T{
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use the preprocessor \fIproc\fP instead of the preprocessor given
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in the
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.CW devices
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file for this printer.
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T}
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_
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-q LPQ N 1 T{
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print the status and queue.
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T}
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_
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-r REVERSE L 1 T{
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this toggles the
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.CW REVERSE
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flag, changing whether or not page reversal should occur in preprocessing.
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Page reversal is needed if a printer delivers pages face up.
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The keyword
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.CW reverse
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can be placed in the
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.I lpclass
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field of the
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.CW devices
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file.
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If a document has already been processed this flag has no effect.
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T}
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_
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-u \fIuser\fP LPUSERID U \fIuser\fP T{
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change the user id that appears on the cover page.
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T}
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_
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-x \fIoffset\fP XOFF N \fIoffset\fP T{
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move the image \fIoffset\fP inches to the right.
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A negative \fIoffset\fP will move the image to the left.
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The \fIoffset\fP may be any reasonable real number.
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T}
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_
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-y \fIoffset\fP YOFF N \fIoffset\fP T{
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same as for
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.CW -x
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except a positive offset will move the image down.
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T}
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_
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.T&
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l l cp-2 lp-2 s
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l l cfCWp-2 lp-2 s.
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.vs -2p
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default setting definition
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N set to the null string (`') initially in \fIlp\fP.
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L set from printer entry in \f(CW\\s-\\n(XPdevices\\s+\\n(XP\fP file.
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U set from the user's environment.
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.vs +2p
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.TE
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.sp
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.ce
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.I "Table 1. Lp Option List"
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.sp
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.ll \\n(LLu
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.KE
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\" .2C
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.NH
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Devices file
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.PP
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The
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.CW devices
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file is found in the spool directory.
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Each line in the file is composed of 12 fields, separated
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by tabs or spaces, that describe the attributes
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of the printer and how it should be serviced.
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Within the
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.CW lp
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command, a shell variable is set for each attribute;
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the following list describes them:
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.IP "\f(CW\s-\n(XPLPDEST\s+\n(XP\fP " 12
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is the name of the device as given to
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.I lp
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with the
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.CW -d
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option
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or as specified by the shell environment variable
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.CW LPDEST
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or as specified by
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the file
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.CW $LPLIB/defdevice .
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This name is used in creating directories and log files that are associated with
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the printers operation.
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.IP "\f(CW\s-\n(XPLOC\s+\n(XP\fP "
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just describes where the printer is physically located.
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.IP "\f(CW\s-\n(XPDEST_HOST\s+\n(XP\fP "
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is the host from which the files are printed.
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Files may be spooled on other machines before being transferred to the
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destination host.
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.IP "\f(CW\s-\n(XPOUT_DEV\s+\n(XP\fP "
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is the physical device name or network address needed by the printer daemon
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to connect to the printer.
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This field depends on the requirements of the daemon and may contain a `\(en'
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if not required.
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.IP "\f(CW\s-\n(XPSPEED\s+\n(XP\fP "
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is the baud rate setting for the port.
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This field depends on the requirements of the daemon and may contain a `\(en'
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if not required.
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.IP "\f(CW\s-\n(XPLPCLASS\s+\n(XP\fP "
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is used to encode minor printer differences.
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The keyword
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.CW reverse
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is used by some of the preprocessors
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to reverse the order the pages are printed to accommodate different output
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trays (either face up or face down).
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The keyword
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.CW nohead
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is used to suppress the header page.
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This is used for special and color printers.
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The keyword
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.CW duplex
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is used to coax double sided output from duplex printers.
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.IP "\f(CW\s-\n(XPLPPROC\s+\n(XP\fP "
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is the command from the
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.CW LPLIB/process
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directory to be used to convert input to a format
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that will be accepted by the device.
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The preprocessor is invoked by the spooler.
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|
.IP "\f(CW\s-\n(XPSPOOLER\s+\n(XP\fP "
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|
is the command from the
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.CW LPLIB/spooler
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|
directory which will select files using the
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.CW SCHED
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command and invoke the
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.CW LPPROC
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command, putting its output
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into the remote spool directory.
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The output is sent directly to the spool directory on the
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destination machine to avoid conflicts when client and
|
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server machines share spool directories.
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|
.IP "\f(CW\s-\n(XPSTAT\s+\n(XP\fP "
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|
is the command from the
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.CW LPLIB/stat
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directory that prints the status of the device and the list of jobs
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|
waiting on the queue for the device.
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|
The status information depends on what is available from the printer
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|
and interface software.
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|
The queue information should be changed to show information
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|
useful in tracking down problems.
|
|
The
|
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.CW SCHED
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command is used to show the jobs in the order
|
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in which they will be printed.
|
|
.IP "\f(CW\s-\n(XPKILL\s+\n(XP\fP "
|
|
is the command from the
|
|
.CW LPLIB/kill
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|
that removes jobs from the queue.
|
|
The jobs to be removed are given as arguments to the
|
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.I lp
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command.
|
|
When possible, it should also abort the currently running job
|
|
if it has to be killed.
|
|
.IP "\f(CW\s-\n(XPDAEMON\s+\n(XP\fP "
|
|
is the command from the
|
|
.CW LPLIB/daemon
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|
that is meant to run asynchronously to remove
|
|
jobs from the queue.
|
|
Jobs may either be passed on to another host or sent to the
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printing device.
|
|
.I Lp
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|
always tries to start a daemon process when one is specified.
|
|
.IP "\f(CW\s-\n(XPSCHED\s+\n(XP\fP "
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|
is the command from the
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|
.CW LPLIB/sched
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|
that is used to present the job names to the
|
|
daemon and stat programs
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|
in some order, e.g., first-in-first-out, smallest first.
|
|
.NH
|
|
Support programs
|
|
.PP
|
|
The following sections describe the basic functions of the programs
|
|
that are found in the subdirectories of
|
|
.CW $LPLIB .
|
|
The programs in a specific directory vary with the
|
|
type of output device or networks that have to be used.
|
|
.NH 2
|
|
Process directory
|
|
.PP
|
|
The
|
|
.CW generic
|
|
preprocessor
|
|
is the default preprocessor for most printers.
|
|
It uses the
|
|
.I file (1)
|
|
command to determine the format of the input file.
|
|
The appropriate preprocessor is then selected to transform the
|
|
file to a format suitable for the printer.
|
|
.PP
|
|
Here is a list of some of the preprocessors and
|
|
a description of their function.
|
|
A complete list of preprocessors and their descriptions can be found in the manual page
|
|
.I lp (8).
|
|
.sp
|
|
.IP \f(CWdvipost\fP 14
|
|
Converts TeX or LaTeX output (\f(CW.dvi\fP files) to PostScript
|
|
.IP \f(CWppost\fP
|
|
Converts UTF text to PostScript.
|
|
The default font is Courier with Lucida fonts filling in
|
|
the remainder of the (available) Unicode character space.
|
|
.IP \f(CWtr2post\fP
|
|
Converts (device independent) troff output for the device type
|
|
.CW utf .
|
|
See
|
|
.CW /sys/lib/troff/font/devutf
|
|
directory for troff font width table descriptions.
|
|
See also the
|
|
.CW /sys/lib/postscript/troff
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|
directory for mappings of
|
|
troff
|
|
.CW UTF
|
|
character space to PostScript font space.
|
|
.IP \f(CWp9bitpost\fP
|
|
Converts Plan 9 bitmaps (see
|
|
.I bitfile (9.6))
|
|
to PostScript.
|
|
.IP \f(CWg3post\fP
|
|
Converts fax (CCITT-G31 format) to PostScript.
|
|
.IP \f(CWhpost\fP
|
|
Does header page processing and page reversal processing, if
|
|
necessary.
|
|
Page reversal is done here so the header page always comes
|
|
out at the beginning of the job.
|
|
Header page processing is very location-dependent.
|
|
.NH 2
|
|
Spool directory
|
|
.PP
|
|
The
|
|
.CW generic
|
|
spooler is responsible for executing the preprocessor
|
|
and directing its output to a file in the printer's queue.
|
|
An additional file is created containing information such as the system name,
|
|
user id, job number, and number of times this job was attempted.
|
|
.PP
|
|
Certain printer handling programs do not require separate
|
|
preprocessing and spooling.
|
|
For such circumstances a
|
|
.CW nospool
|
|
spooler is available that just executes the preprocessing program.
|
|
The processing and spooling functions are assumed by this program and the output is sent to
|
|
.CW OUT_DEV
|
|
or standard output if
|
|
.CW OUT_DEV
|
|
is '-'.
|
|
.PP
|
|
The
|
|
.CW pcclone
|
|
spooler is used to send print jobs directly to a printer connected
|
|
to a 386 compatible printer port (See
|
|
.I lpt (3)).
|
|
.NH 2
|
|
Stat directory
|
|
.PP
|
|
The function of the shell scripts in the
|
|
.CW stat
|
|
directory is to present status information about the
|
|
printer and its queue.
|
|
When necessary, the
|
|
.CW stat
|
|
scripts may be designed
|
|
to return information about the local queue as well as the remote queue.
|
|
This is not done on Plan 9 because many systems share the same queue directory.
|
|
The scheduler is used to print the queue in the order in which the jobs
|
|
will be executed.
|
|
.NH 2
|
|
Kill directory
|
|
.PP
|
|
The
|
|
.CW kill
|
|
scripts receive command line arguments passed to them by
|
|
.I lp
|
|
and remove the job and id files which match the arguments
|
|
for the particular queue.
|
|
When a job is killed, the generic kill procedure:
|
|
.IP 1)
|
|
kills the daemon for this queue if the job being killed
|
|
is first in the queue,
|
|
.IP 2)
|
|
removes the files associated with the job from the queue,
|
|
.IP 3)
|
|
attempts to restart the daemon.
|
|
.NH 2
|
|
Daemon directory
|
|
.PP
|
|
The
|
|
.CW daemon
|
|
shell scripts are the last to be invoked by
|
|
.I lp
|
|
if the
|
|
.CW -Q
|
|
option has not been given.
|
|
The daemon process is executed asynchronously
|
|
with its standard output and standard error appended to
|
|
the printer log file.
|
|
The log file is described in a subsequent section.
|
|
Because the daemon runs asynchronously, it must
|
|
catch signals that could cause it to terminate abnormally.
|
|
The daemon first checks to see that it is the only one running
|
|
by using the
|
|
.CW LOCK
|
|
program found in the
|
|
.CW /$cputype/bin/aux
|
|
directory.
|
|
The
|
|
.CW LOCK
|
|
command creates a
|
|
.CW LOCK
|
|
file in the printer's queue directory.
|
|
The daemon then executes the scheduler to obtain the name of the
|
|
next job on the queue.
|
|
.PP
|
|
The processing of jobs may entail transfer to another host
|
|
or transmission to a printer.
|
|
The details of this are specific to the individual daemons.
|
|
If a job is processed without error, it is removed from the queue.
|
|
If a job does not succeed, the associated files may be
|
|
moved to a printer specific directory in
|
|
.CW $LPLIB/prob .
|
|
In either case, the daemon can make an entry in the printer's
|
|
log file.
|
|
Before exiting, the daemon should clean up lock files by calling
|
|
.CW UNLOCK .
|
|
.PP
|
|
Several non-standard daemon programs have been designed
|
|
to suit various requirements and whims.
|
|
One such program announces job completion and empty paper trays
|
|
by causing icons to appear in peoples'
|
|
.CW seemail
|
|
window.
|
|
Another, using a voice synthesizer, makes verbal announcements.
|
|
Other daemons may be designed to taste.
|
|
.NH 2
|
|
Sched directory
|
|
.PP
|
|
The scheduler must decide which job files should be executed and
|
|
in what order.
|
|
The most commonly used scheduler program is
|
|
.CW FIFO ,
|
|
which looks like this:
|
|
.P1
|
|
ls -tr $* | sed -n -e 's/.* *//' \e
|
|
-e '/^[0-9][0-9]*\.[1-9][0-9]*$/p'
|
|
.P2
|
|
This lists all the job files in this printer's queue in modification
|
|
time order.
|
|
Jobs entering the queue have a dot (.) prefixed to their name
|
|
to keep the scheduler from selecting them before they are complete.
|
|
.NH
|
|
Where Things Go Wrong
|
|
.PP
|
|
There are four directories where
|
|
.I lp
|
|
writes files.
|
|
On the Plan 9 release these directories may be found
|
|
in a directory on a scratch filesystem that is not
|
|
backed-up.
|
|
This directory is
|
|
.CW /n/emelieother/lp .
|
|
It is built on top of a file system
|
|
.CW other
|
|
that is mounted on the file server
|
|
.CW emelie .
|
|
The four directories in
|
|
this scratch directory
|
|
are
|
|
.CW log ,
|
|
.CW prob ,
|
|
.CW queue ,
|
|
and
|
|
.CW tmp .
|
|
.I Lp
|
|
binds (see
|
|
.I bind (1))
|
|
the first three into the directory
|
|
.CW /sys/lib/lp
|
|
for its processes and their children.
|
|
The
|
|
.CW tmp
|
|
directory is bound to the
|
|
.CW /tmp
|
|
directory so that the lp daemons, which run as user `none',
|
|
may write into this directory.
|
|
.PP
|
|
On any new installation, it is important that these directories
|
|
be set up and that the
|
|
.I /rc/bin/lp
|
|
command be editted to reflect the change.
|
|
If you do not have a scratch filesystem for these directories,
|
|
create the four directories
|
|
.CW log ,
|
|
.CW prob ,
|
|
.CW queue ,
|
|
and
|
|
.CW tmp
|
|
in
|
|
.CW $LPLIB
|
|
.CW (/sys/lib/lp)
|
|
so that they are writable by anyone.
|
|
.NH 2
|
|
Log directory
|
|
.PP
|
|
The log files for a particular
|
|
.I printer
|
|
appear in a subdirectory of the spool directory
|
|
\f(CWlog\fP/\fIprinter\fP.
|
|
There are currently two types of log files.
|
|
One is for the daemon to log errors and successful completions
|
|
of jobs.
|
|
These are named
|
|
.I printer.day
|
|
where
|
|
.I day
|
|
is the three letter abbreviation for the day of the week.
|
|
These are overwritten once a week to avoid the need for regular
|
|
cleanup.
|
|
The other type of log file contains the status of the printer and
|
|
is written by the program that communicates with the printer itself.
|
|
These are named
|
|
\fIprinter\fP.\f(CWst\fP.
|
|
These are overwritten with each new job and are saved in the
|
|
.CW $LPLIB/prob
|
|
directory along with the job under circumstances described below.
|
|
When a printer does not appear to be functioning these files are the
|
|
place to look first.
|
|
.NH 2
|
|
Prob directory
|
|
.PP
|
|
When a job fails to produce output,
|
|
the log files should be checked for any obvious problems.
|
|
If none can be found, a directory with full read and write permissions
|
|
should be created with the name of the printer in the
|
|
.CW $LPLIB/prob
|
|
directory.
|
|
Subsequent failure of a job will cause the daemon to leave a
|
|
copy of the job and the printer communication log in
|
|
\f(CW$LPLIB/prob/\fP\fIprinter\fP
|
|
directory.
|
|
It is common for a printer to enter states from which
|
|
it cannot be rescued except by manually cycling the power on the printer.
|
|
After this is done the print daemon should recover by itself
|
|
(give it a minute).
|
|
If it does not recover, remove the
|
|
.CW LOCK
|
|
file from the printer's spool directory to kill the daemon.
|
|
The daemon will have to be restarted by sending another job
|
|
to the printer.
|
|
For PostScript printers just use:
|
|
.P1
|
|
echo '%!PS' | lp
|
|
.P2
|
|
.NH 2
|
|
Repairing Stuck Daemons
|
|
.PP
|
|
There are conditions that occur which are not handled
|
|
by the daemons.
|
|
One such problem can only be described as the printer entering a
|
|
comatose state.
|
|
The printer does not respond to any messages sent to it.
|
|
The daemon should recover from the reset and an error message
|
|
will appear in the log files.
|
|
If all else fails, one can kill the first job in the queue
|
|
or remove the
|
|
.CW LOCK
|
|
file from the queue directory.
|
|
This will kill the daemon, which will have to be restarted.
|
|
.NH
|
|
Interprocessor Communication
|
|
.PP
|
|
A Plan 9 CPU server can be set up as a printer's spooling host.
|
|
That is, the machine where jobs are spooled and from which those jobs
|
|
are sent directly to the printer.
|
|
To do this, the CPU must listen on TCP port 515 which is the well known
|
|
port for the BSD line printer daemon.
|
|
The file
|
|
.CW /rc/bin/service/tcp515
|
|
is executed when a call comes in on that port.
|
|
The Plan 9
|
|
.CW lpdaemon
|
|
will accept jobs sent from BSD LPR/LPD systems.
|
|
The
|
|
.CW /$cputype/bin/aux/lpdaemon
|
|
command is executed from the service call and it accepts print jobs, requests for status,
|
|
and requests to kill jobs.
|
|
The command
|
|
.CW /$cputype/bin/aux/lpsend
|
|
is used to send jobs
|
|
to other Plan 9 machines and is usually called from
|
|
within a spooler or daemon script.
|
|
The command
|
|
.CW /$cputype/bin/aux/lpdsend
|
|
is used to send jobs
|
|
to machines and printers that use the BSD LPR/LPD protocol and is also usually called from
|
|
within a spooler or daemon script.
|
|
.NH
|
|
Acknowledgements
|
|
.PP
|
|
Special thanks to Rich Drechsler for supplying and maintaining most of
|
|
the PostScript translation and interface programs,
|
|
without which
|
|
.I lp
|
|
would be an empty shell.
|
|
Tomas Rokicki provided the
|
|
TeX
|
|
to PostScript
|
|
translation program.
|
|
.NH
|
|
References
|
|
.LP
|
|
[Camp86] Ralph Campbell,
|
|
``4.3BSD Line Printer Spooler Manual'', UNIX System Manager's Manual,
|
|
May, 1986, Berkeley, CA
|
|
.br
|
|
[RFC1179] Request for Comments: 1179, Line Printer Daemon Protocol, Aug 1990
|
|
.br
|
|
[Sys5] System V manual, date unknown
|