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From: tony@artecon.UUCP
Newsgroups: comp.unix.questions,comp.unix.wizards
Subject: Re: Filters for the BSD print spooling system
Message-ID: <400@artecon.artecon.UUCP>
Date: Tue, 31-Mar-87 11:16:03 EST
Article-I.D.: artecon.400
Posted: Tue Mar 31 11:16:03 1987
Date-Received: Fri, 3-Apr-87 06:37:09 EST
References: <111@coke.UUCP>
Reply-To: tony@artecon.UUCP (Anthony D. Parkhurst)
Organization: artecon
Lines: 87
Keywords: sun bsd print spooler printer filter
Xref: utgpu comp.unix.questions:1576 comp.unix.wizards:1618

In article <111@coke.UUCP> robert@coke.UUCP (Robert Claeson) writes:
>I'm not really sure whether this should go to comp.unix.questions
>or comp.unix.wizards, so I send it to both.

     When in doubt, send it to comp.unix.questions.  IF no response,
(or responses that say it's a wizard question), then post it to
the wizards group.  (At least this is the rule I remember).

>installed it as if (input(?) filter) and of (output filter), only

     I haven't used 'if' before, but my manual says it is for
accounting?  I suppose 'input' could be derived.

>lpd expects the output filter (the one which prints the banner page)

     You can get the banner without an output filter.

Anyways here are a few things to consider:

	1)  Always use absolute path names.  When lpd is spawned by rc
	    at boot time, it on many systems has an empty environment
	    (ie. no PATH)

	2)  Make sure that the error logging file exists.  If your
	    error file is /usr/adm/lpd-errs (or whatever), that file
	    has to exist, or the errors will not be logged.  This
	    can be a big help, it will freqently tell you what the
	    problem is.  However, when you are done with it remove it
	    because it can grow quickly while not being monitored.

	3)  (wait, there is no 3)

Here are a few points from one of my manuals:

	RE: fields in printcap:

		if:  Output filter that can do accounting

		of:  Output filter, if 'if' is specified, 'of' is only
		     used for the banner page.

		tf,cf,vf: other output filters.

		lf: error logging file

	(The point here is that not all filters are used on each job)
	You don't NEED an 'if' AND an 'of'.  The tf,cf,and vf are used
	if certain flags are passed.  I don't see the use of using 
	BOTH 'if' and 'of' when they are the SAME filter (as you specified
	above).

On filters themselfs:

	Filters are spawned by lpd with stdin the data, stdout the printer
	and stderr the file specified by 'lf'.

	Filters should return '0' exit code for success, '1' if job
	should be reprinted, and '2' if job should be thrown away.

	SIGINT is sent to all the processes when lprm is issued to remove
	a job.

	Arguments passed to filters:

		of filter:  ofilter -wwidth -llength
			(see 'pw' and 'pl' in printcap)
			(I wonder how 'of' can print the banner w/o names)
		
		if filter: 

	ifilter [-c] -wwidth -llength -iindent -n login -h host accounting_file

		-c is present when -l is used on the lpr command.

	All other filters:

	filter -xwidth -ylength -n login -h host accounting_file

	   (see 'px' and 'py' in printcap)

Hope this helps

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