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- .\" must display the following acknowledgement:
- .\" This product includes software developed by the University of
- .\" California, Berkeley and its contributors.
- .\" 4. Neither the name of the University nor the names of its contributors
- .\" may be used to endorse or promote products derived from this software
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- .\" @(#)5.t 6.6 (Berkeley) 4/17/91
- .\"
- .NH 1
- Output filter specifications
- .PP
- The filters supplied with 4.3BSD
- handle printing and accounting for most common
- line printers, the Benson-Varian, the wide (36") and
- narrow (11") Versatec printer/plotters. For other devices or accounting
- methods, it may be necessary to create a new filter.
- .PP
- Filters are spawned by \fIlpd\fP
- with their standard input the data to be printed, and standard output
- the printer. The standard error is attached to the
- .B lf
- file for logging errors or \fIsyslogd\fP may be used for logging errors.
- A filter must return a 0 exit
- code if there were no errors, 1 if the job should be reprinted,
- and 2 if the job should be thrown away.
- When \fIlprm\fP
- sends a kill signal to the \fIlpd\fP process controlling
- printing, it sends a SIGINT signal
- to all filters and descendents of filters.
- This signal can be trapped by filters that need
- to do cleanup operations such as
- deleting temporary files.
- .PP
- Arguments passed to a filter depend on its type.
- The
- .B of
- filter is called with the following arguments.
- .DS
- \fIfilter\fP \fB\-w\fPwidth \fB\-l\fPlength
- .DE
- The \fIwidth\fP and \fIlength\fP values come from the
- .B pw
- and
- .B pl
- entries in the printcap database.
- The
- .B if
- filter is passed the following parameters.
- .DS
- \fIfilter\fP [\|\fB\-c\fP\|] \fB\-w\fPwidth \fB\-l\fPlength \fB\-i\fPindent \fB\-n\fP login \fB\-h\fP host accounting_file
- .DE
- The
- .B \-c
- flag is optional, and only supplied when control characters
- are to be passed uninterpreted to the printer (when using the
- .B \-l
- option of
- .I lpr
- to print the file).
- The
- .B \-w
- and
- .B \-l
- parameters are the same as for the
- .B of
- filter.
- The
- .B \-n
- and
- .B \-h
- parameters specify the login name and host name of the job owner.
- The last argument is the name of the accounting file from
- .IR printcap .
- .PP
- All other filters are called with the following arguments:
- .DS
- \fIfilter\fP \fB\-x\fPwidth \fB\-y\fPlength \fB\-n\fP login \fB\-h\fP host accounting_file
- .DE
- The
- .B \-x
- and
- .B \-y
- options specify the horizontal and vertical page
- size in pixels (from the
- .B px
- and
- .B py
- entries in the printcap file).
- The rest of the arguments are the same as for the
- .B if
- filter.
-