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1.1 root 1: .so ../ADM/mac
2: .XX lp 603 "A Guide to the Lp Printer Spooler"
3: .nr dP 1
4: .nr dV 1.5p
5: .ND
6: .TL
7: A Guide to the Lp
8: Printer Spooler
9: .AU
10: P. Glick
11: .AI
12: AT&T Bell Laboratories
13: Murray Hill, New Jersey 07974
14: .AB
15: .PP
16: .I Lp
17: is a collection of programs used to provide an easy-to-use
18: interface for printing a variety of document types on a variety
19: of printers.
20: .I Lp
21: is meant to be the glue that connects various document language
22: translators and printer communication programs together so that
23: the users may have a consistent view of printers.
24: Most of the glue
25: is shell script, which can be easily modified.
26: The user need not
27: specify options to get sensible output in most cases.
28: .I Lp
29: is described here
30: so that others may make additions and changes.
31: Only the shell scripts, or glue, are described here.
32: .AE
33: .2C
34: .NH
35: Introduction
36: .PP
37: .I Lp
38: is used to format and print data on a variety of output devices.
39: The need for
40: .I lp
41: was rooted in the inability of other printer spoolers to do simple
42: tasks without a great deal of user specification of options.
43: At the time
44: .I lp
45: was written, there were several printer
46: languages, such as ImPress and P\s-2OST\s+2S\s-2CRIPT\s+2 and
47: an internally developed printer that would accept
48: .I troff
49: output.
50: A great deal of what underlies
51: .I lp
52: is taken from other systems.
53: The important features of this system are that most of the programs
54: are easily modified shell scripts and the user need not
55: fuss with the large amount of underlying software developed by others.
56: .I Lp
57: runs under several flavors of the
58: .UX
59: Operating System
60: and uses both Datakit and Ethernet to transport data between machines.
61: .PP
62: Text, graphics, and formatted text files are appropriately processed and
63: placed into a spool directory from which they are taken to be printed.
64: Additional functions include checking the status of a printer queue
65: and removing jobs from the printer queue.
66: .PP
67: All files associated with
68: .I lp
69: reside in the spool directory
70: (usually \f(CW/usr/spool/lp\fP),
71: except for the
72: .I lp
73: command itself which usually resides in \f(CW/usr/bin\fP.
74: The spool directory is defined within the
75: .I lp
76: command by the shell variable \f(CWLPSPOOL\fP.
77: In the remainder of this document, file names may be specified
78: with this shell variable as their root.
79: .NH
80: Usage
81: .PP
82: .I Lp
83: requires that an output device be specified
84: before it will process input.
85: This can be done in any of three ways described here in increasing order
86: of precedence.
87: .SP .5
88: .TA 5
89: \(em The file
90: .CW $LPSPOOL/defdevice
91: may contain the name of a default output device.
92: This may not be practical for environments where
93: there are many printers
94: and the default device need not be specified.
95: .SP .5
96: \(em The user's environment variable
97: .CW LPDEST
98: may be set to the name of the device to be used.
99: This is often a more practical solution when there are several printers
100: available.
101: This overrides a
102: .CW defdevice
103: specification.
104: .SP .5
105: \(em The
106: .CW "-d printer"
107: option to the
108: .I lp
109: command specifies
110: .I printer
111: as the device to which output should be directed, overriding the
112: previous two specifications.
113: .PP
114: If
115: .I printer
116: is
117: .CW ? ,
118: a list of printers and other information in the
119: .CW devices
120: file is printed, as shown in Figure 1.
121: .1C
122: .KF
123: .P1 20n
124: $ lp -d"?"
125: device location host class
126: dp 2C-504 nj/astro/coma post300+reverse
127: imagen1 st8_fl1 nj/phone/sid imagen/2.2+reverse
128: po 2C-579 nj/astro/pipe dumb
129: ps2c364 2C-364 nj/phone/sid post300+reverse
130: ps71 2D-154 nj/phone/gauss post300+reverse
131: ps83 st8_fl3 nj/phone/gauss post300+reverse
132: psu 2C-501 nj/astro/coma post300+reverse
133: .
134: .
135: .
136: $
137: .P2
138: .ce
139: \fBFigure 1.\fR Sample listing of installed printers.
140: .KE
141: .SP
142: .2C
143: .PP
144: Normal
145: .I troff
146: output can be printed with
147: .P1
148: $ troff -ms lp.ms | lp -ddp
149: .P2
150: .NE 3
151: LaTex (and analogously Tex) documents are printed in two steps:
152: .P1
153: $ latex lp.tex
154: .
155: .
156: $ lp -dpsu lp.dvi
157: .
158: .
159: $
160: .P2
161: LaTeX
162: produces a `.dvi' file and
163: does not permit the use of a pipe
164: connection to the standard input of
165: .I lp .
166: In both these cases I have explicitly specified a destination
167: because my
168: .CW LPDEST
169: variable is set to a printer near my office, which I use infrequently.
170: Although this doesn't make a great deal of sense, it is useful for
171: the purpose of these examples.
172: .PP
173: To look at the status and queue of a device:
174: .P1 0
175: $ lp -dpsu -q
176: status:
177: %%[ status: idle ]%%
178: sending file psu/29436.1
179: %%[ status: busy; source: serial 25 ]%%
180:
181: queue on nj/astro/coma:
182: job user try size
183: gauss29436.1 pg 0 17454
184: coma17565.1 ches 1 49995
185: $
186: .P2
187: This command prints the status and queue on the local
188: and remote hosts.
189: The format of the status and queue printout is up to the administrator.
190: .PP
191: The job started above can be killed as follows
192: (where the output is too long for the column, it has been folded at the \*(cr):
193: .P1 0
194: $ lp -dpsu -k gauss29436.1
195: gauss29436.1 removed from psu queue\*(cr
196: on nj/astro/coma
197: .P2
198: If you wish to kill a job on the queue but the job has begun to print,
199: you then have to turn the printer off and on to kill the currently
200: printing job.
201: This may be fixed someday.
202: .NH
203: Options
204: .PP
205: There are options available to modify the way in which a job is handled.
206: It is the job of the
207: .I lp
208: programs to convert the option settings so they can be used by each of the
209: different translation and interface programs.
210: Not all options are applicable to all printer environments.
211: Table 1 lists the standard
212: .I lp
213: options, the shell variable settings and description of the options.
214: .1C
215: .KF
216: .SP
217: .TS
218: center;
219: c | c s s | c
220: c | c c c | c
221: lfCWw(.7i)| lfCWw(.6i) cfCWw(.4i) cfCWw(.6i)| lw(2.8i).
222: =
223: option shell variable action
224: \^ name default set \^
225: _
226: -D DEBUG N -D turn on debugging mode.
227: -H NOHEADER N 1 suppress header page.
228: -L LAND N 1 make long page dimension horizontal.
229: -M \fImach\fP LPMACHID N \fImach\fP set the source machine name.
230: -Q QONLY N 1 do not execute daemon; for debugging purposes.
231: -c \fIn\fP COPIES N \fIn\fP number of copies to be printed.
232: -d \fIprinter\fP LPDEST U \fIprinter\fP set job destination; override other settings.
233: -f \fIfont.pt\fP FONT N \fIfont\fP set font style and point size for printing.
234: POINT N \fIpt\fP
235: -i \fIn\fP IBIN N \fIn\fP T{
236: select alternate paper tray.
237: The argument given is dependent on the printer type,
238: although some effort is made in the process files to make `2'
239: an acceptable argument.
240: T}
241: -k KILLFLAG 0 1 T{
242: take non-option arguments as job numbers to be removed from queue.
243: T}
244: -l \fIn\fP LINES N \fIn\fP T{
245: for printed data, the number of lines per logical page.
246: T}
247: -m \fIf\fP MAG N \fIf\fP T{
248: magnify the image by a factor \fIf\fP.
249: The factor should be a positive real number.
250: T}
251: -n \fIn\fP NPAG N \fIn\fP T{
252: put \fIn\fP logical pages on a single physical page.
253: A simple algorithm is used to pack the pages.
254: T}
255: -o \fIlist\fP OLIST N \fIlist\fP T{
256: print only those pages specified in the list.
257: The list may be a sequence of numbers or ranges separated by commas.
258: A range is a pair of numbers separated by a hyphen.
259: T}
260: -p \fIproc\fP LPPROC L \fIproc\fP T{
261: use the preprocessor \fIproc\fP instead of the preprocessor given
262: in the
263: .CW devices
264: file for this printer.
265: T}
266: -q LPQ N 1 T{
267: print the status and queue.
268: T}
269: -r REVERSE L - T{
270: this toggles the
271: .CW REVERSE
272: flag changing whether or not page reversal should occur in preprocessing.
273: Page reversal is needed if a printer delivers pages face up.
274: The keyword
275: .CW reverse
276: can be placed in the
277: .I lpclass
278: field of the
279: .CW devices
280: file.
281: If a document has already been processed this flag has no effect.
282: T}
283: -u \fIuser\fP LPUSERID U \fIuser\fP T{
284: change the user id that appears on the cover page to \fIuser\fP.
285: T}
286: -x \fIoffset\fP XOFF N \fIoffset\fP T{
287: move the image \fIoffset\fP inches to the right.
288: A negative \fIoffset\fP will move the image to the left.
289: The \fIoffset\fP may be any reasonable real number.
290: T}
291: -y \fIoffset\fP YOFF N \fIoffset\fP T{
292: same as for \f(CW-x\fP except a positive offset will move the image down.
293: T}
294: _
295: .T&
296: l l cp-2 lp-2 s
297: l l cfCWp-2 lp-2 s.
298: .vs -2p
299: default setting definition
300: N set to the null string (``'') initially in \fIlp\fP.
301: L set from printer entry in \f(CWdevices\fP file.
302: U set from the users environment.
303: .vs +2p
304: .TE
305: .SP
306: .ce
307: \fBTable 1. \fILp\fR Option List
308: .SP 4
309: .KE
310: .2C
311: .NH
312: .CW devices
313: file
314: .PP
315: The
316: .CW devices
317: file is found in the spool directory.
318: Each line in the file is composed of 12 fields which describe the attributes
319: of the printer and how it should be serviced.
320: The following list gives the shell variable set, and a description of
321: each of the attributes.
322: .IP "\f(CWLPDEST\fP "
323: is the name of the device as given to
324: .I lp
325: with the
326: .CW -d
327: option
328: or as specified by the users shell environment variable
329: .CW LPDEST
330: or as specified by
331: the file
332: .CW $LPSPOOL/defdevice .
333: This name is used in creating directories and log files that are associated with
334: the printers operation.
335: .IP "\f(CWLOC\fP "
336: is only used to describe where the printer is located.
337: .IP "\f(CWDEST_HOST\fP "
338: is the host from which the files are printed.
339: Files may be spooled on other machines before being transferred to the
340: destination host.
341: .IP "\f(CWOUT_DEV\fP "
342: is the physical device name or network address needed by the printer daemon
343: to connect to the printer.*
344: .FS
345: * This field depends on the requirements of the daemon and may contain a `\(en'
346: if not required.
347: .FE
348: .IP "\f(CWSPEED\fP "
349: is the baud rate setting for the port.*
350: .IP "\f(CWLPCLASS\fP "
351: is used to distinguish minor printer differences.
352: For example, the keyword `reversal' is used by some of the preprocessors
353: to reverse the order the pages are printed to accommodate different output
354: trays (either face up or face down).
355: .IP "\f(CWLPPROC\fP "
356: specifies the default preprocessor to be used to convert input to a format
357: which will be accepted by the device.
358: The preprocessor is invoked by the spooler.
359: .IP "\f(CWSPOOLER\fP "
360: is the process used to invoke the preprocessor and its output in the local
361: spool directory.
362: .IP "\f(CWSTAT\fP "
363: prints the status of the device (whatever that means!) and the list of jobs
364: waiting on the queue for this device.
365: The status information depends on what is available from the printer
366: and interface software.
367: The queue information has been changed several times to show information
368: useful in tracking down problems.
369: The scheduler is used to show the jobs in the order
370: in which they will be printed.
371: .IP "\f(CWKILL\fP "
372: removes jobs from the queue.
373: The jobs to be removed are given as arguments to the
374: .I lp
375: command.
376: When possible, it should also abort the currently running job
377: if it has been killed.
378: .IP "\f(CWDAEMON\fP "
379: is a process that is meant to run asynchronously to remove
380: jobs from the queue.
381: Jobs may either be passed on to another host or sent to the
382: printing device.
383: .I Lp
384: always tries to start a daemon process when one is specified.
385: .IP "\f(CWSCHED\fP "
386: is used to present the job names to the daemon and stat programs
387: in some order, e.g. first-in-first-out, smallest first.
388: .NH
389: Support programs
390: .PP
391: The following sections describe the basic function of the programs
392: that are found in the subdirectories of
393: .CW LPSPOOL .
394: The programs in a specific directory vary the
395: type of output device or networks that have to be dealt with or some
396: special set of user requirements.
397: .NH 2
398: .CW process
399: Files
400: .PP
401: The
402: .CW generic
403: preprocessor
404: is the default preprocessor for most printers.
405: It uses the
406: .I file (1)
407: command to determine the format of the input file.
408: The appropriate preprocessor is then selected to transform the
409: file to a format suitable for the printer.
410: .PP
411: Table 2 shows the names of programs that convert input formats (first column),
412: to output formats (top row).
413: .1C
414: .KF
415: .TS
416: center box;
417: c || c | c | c
418: c || cI | cI | cI.
419: P\s-2OST\s+2S\s-2CRIPT\s+2 Impress T{
420: Canon
421: .br
422: (obsolete)
423: T}
424: =
425: text, listings ppost daisimag can
426: _
427: troff output dpost dimp dcan
428: _
429: Latex output (.dvi files) dvipost dviimp \(em
430: _
431: bitmaps [see \fIbitfile\fR(9.5)] bpost bimp bcan
432: _
433: Tektronix graphics tpost tekimag tcan
434: .TE
435: .ce
436: \fBTable 2.\fP
437: .SP 2
438: .KE
439: .2C
440: .PP
441: There are also several interface routines here used to send
442: files to, e.g. the color P\s-2OST\s+2S\s-2CRIPT\s+2 printer
443: and the
444: .SM LINOTRONICS
445: P\s-2OST\s+2S\s-2CRIPT\s+2 phototypesetter.
446: .NH 2
447: .CW spool
448: Files
449: .PP
450: The generic spooler is responsible for executing the preprocessor
451: and directing its output to a file in the printers queue.
452: An additional file is created containing information such as the system name,
453: user id, job number, and number of times this job was attempted.
454: The format of the id file has been changed from time to time
455: to assist with debugging.
456: .PP
457: Certain printer handling programs do not require separate preprocessing
458: and spooling.
459: For such circumstances a
460: .CW nospool
461: spooler is available which simply executes the preprocessing program.
462: The processing and spooling functions are assumed by this program.
463: .NH 2
464: .CW stat
465: Files
466: .PP
467: The function of these files is to present status information about the
468: printer and its queue.
469: Because
470: .I lp
471: often works over a network connection, the stat function is designed
472: to return information about the local queue as well as the remote queue.
473: The scheduler is used to print the queue in the order in which the jobs
474: will be executed.
475: The various commands in the
476: .CW stat
477: directory differ only in the means in which they access different networks.
478: .NH 2
479: .CW kill
480: Files
481: .PP
482: These programs receive command line arguments passed to them by
483: .I lp
484: and remove the job and id files which match the arguments
485: from the particular queue.
486: .NH 2
487: .CW daemon
488: Files
489: .PP
490: The
491: daemon is the last program invoked by
492: .I lp
493: if the \f(CW-Q\fP option has not been given.
494: The daemon process is executed asynchronously
495: with its standard output and standard error appended to
496: the printer log file.
497: The log file is described in a subsequent section.
498: Because the daemon runs asynchronously, it must
499: catch signals that could cause it to terminate abnormally.
500: The daemon first checks to see that it is the only one running
501: by using the
502: .CW LOCK
503: program found in the daemon directory.
504: The daemon then executes the scheduler to obtain the name of the
505: next job on the queue.
506: .PP
507: The processing of jobs may entail transfer to another host
508: or transmission to a printer.
509: The details of this are specific to the individual daemons.
510: If a job is processed without error, it is removed from the queue.
511: If a job does not succeed, the associated files may be
512: moved to a printer specific directory in
513: \f(CW$LPSPOOL/prob\fP.
514: In either case, the daemon can make an entry in the printer's
515: log file.
516: Before exiting, the daemon should clean up lock files by calling
517: .SM \fIUNLOCK\fP .
518: .PP
519: The
520: .SM \fILOCK\fP
521: command creates a
522: .CW LOCK
523: file in the printer's queue and makes a link to a file called
524: .CW LINK .
525: The locking mechanism could be improved but there have been very
526: few failures.
527: .PP
528: Several non-standard daemon programs have been designed
529: to suite various requirements and whims.
530: One such program announces job completion and empty paper trays
531: by causing icons to appear in peoples'
532: .I vismon (9.1)
533: window.
534: Another, using a voice synthesizer, makes verbal announcements.
535: Other daemons may be designed to taste.
536: .NH 2
537: .CW sched
538: Files
539: .PP
540: The scheduler must decide which job files should be executed and
541: in what order.
542: The most commonly used scheduler algorithm is FIFO, which looks like this:
543: .P1 0
544: ls -tr $* | sed -n -e 's/.* *//' \e
545: -e '/^[0-9][0-9]*\.[1-9][0-9]*$/p'
546: .P2
547: This lists all the job files in this printer's queue in modification
548: time order.
549: Jobs entering the queue have a dot (.) prepended to their name
550: to keep the scheduler from selecting them before they are complete.
551: .NH
552: When Thing Go Wrong
553: .NH 2
554: .CW log
555: Files
556: .PP
557: The log files for a particular
558: .I printer
559: appear in a subdirectory of the spool directory
560: .CW log/printer .
561: There are currently two types of log files that appear
562: here.
563: One is for the daemon to log errors and successful completions
564: of jobs.
565: These are named
566: .I printer.day
567: where day is the three letter abbreviation for the day of the week.
568: These are overwritten once a week to avoid the need for regular
569: cleanup.
570: The other type of log file contains the status of the printer and
571: is written by the program that communicates with the printer itself.
572: These are named
573: .I printer.st .
574: These are overwritten with each new job and are saved in the
575: .I prob
576: directory along with the job under circumstances described below.
577: When a printer does not appear to be functioning these files are the
578: place to look first.
579: .NH 2
580: .I prob
581: Files
582: .PP
583: When a job fails to produce output,
584: the log files should be checked for any obvious problems.
585: If none can be found, a directory with full read and write permissions
586: should be created with the name of the printer in the
587: .CW $LPSPOOL/prob
588: directory.
589: Subsequent failure of that job will cause the daemon to leave a
590: copy of the job and the printer communication log in the
591: printers
592: .I prob
593: directory.
594: It is not uncommon for a printer to enter states from which
595: it cannot be rescued except by manually resetting it.
596: .NH 2
597: Repairing Stuck Daemons
598: .PP
599: There are two failure conditions that occur which are not handled
600: by the daemons.
601: .PP
602: One problem can only be described as the printer entering a
603: comatose state.
604: The printer does not respond to any messages sent to it.
605: The daemon should recover from the reset and an error message
606: will appear in the log files.
607: .PP
608: The second problem is more insidious.
609: When communicating with a printer directly connected to Datakit,
610: or when transferring files between a remote and local host over
611: Datakit,
612: the Datakit channel can become
613: frozen and the I/O process hangs.
614: The I/O process must be killed and another must be allowed to start
615: up.
616: The ultimate cure for this problem lies in another domain.
617: .......
618: .NH
619: Interprocessor Communication
620: .PP
621: When a Tenth Edition
622: .UX
623: System is first being set up as a printer host,
624: two files need to be edited.
625: (Sample lines are shown in Figure 2.)
626: .CW /usr/ipc/lib/serv.local
627: needs to define the
628: .I lp
629: service.
630: Authorization lines need to be added to
631: .CW /usr/ipc/lib/auth.local ,
632: permitting certain machines
633: (in this case any machine on the
634: .CW alpha
635: or
636: .CW beta
637: Datakit nodes) to use the
638: .I lp
639: service as the user
640: .CW daemon
641: on this machine.
642: The function of all these lines is explained in more detail in
643: |reference(latest ipc presotto).
644: .1C
645: .KF
646: .P1 10n
647: /usr/ipc/lib/serv.local:
648: .sp .3
649: #service actions
650: lp v9auth+args+cmd(/usr/bin/lp)
651:
652: /usr/ipc/lib/auth.local:
653: .sp .3
654: #service remote-hosts rem-uid local-uid
655: lp dk!nj/(alpha|beta)/.* .* daemon
656: .P2
657: .SP
658: .ce
659: \fBFigure 2.\fR IPC configuration lines
660: .KE
661: .2C
662: .PP
663: The use of
664: .I lp
665: over Ethernet
666: is either more complicated or more restricted in the way
667: .I lp
668: can be used.
669: Because
670: .I lp
671: does not run with special setuid permissions, users must have
672: permission to execute the command remotely.
673: Otherwise, a special program
674: would have to be written to handle the I/O setup for the
675: .I lp
676: program.
677: .NH
678: Acknowledgements
679: .PP
680: Special thanks to Rich Drechsler for supplying and maintaining all
681: the P\s-2OST\s+2S\s-2CRIPT\s+2 translation and interface programs,
682: without which
683: .I lp
684: would be an empty shell.
685: Howard Trickey provided the
686: T\s-2E\s+2X
687: to P\s-2OST\s+2S\s-2CRIPT\s+2
688: translation program.
689: .NH
690: References
691: .LP
692: |reference_placement
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