Ubuntu Manpage: magicfilter - automatic configurable printer filter

NAME

       magicfilter - automatic configurable printer filter

SYNOPSIS

       magicfilter config-file [-c] [-n user] [-h host] [-iindent] [--debug] [other-options]

DESCRIPTION

magicfilter is an extensible and customizable automatic printer filter. It selects an appropriate
conversion technique for the input data by seeking for magic numbers, and then utilizing the appropriate
conversion utility.

magicfilter is primarily intended for use as the ``input filter'' by the lpd print spooler. The options
accepted by magicfilter are exactly the ones passed to the input filter by lpd.

OPTIONS
Typically magicfilter will be invoked by lpd and hence provided the right options automatically. This
list is included for reference only.

Note that only the -n and -h options may have spaces between the option letter and the option value.

-c Copy the input to the output without any conversion whatsoever (used by lpd whenever the -l option
is passed to the lpr program).

-nuser, -n user
The login name of the user who submitted the job. Available to subfilters as $LPUSER. If the
user has an associated GECOS entry it will be available as $LPUSERNAME.

-hhost, -h host
The host on which the job was submitted. Available to subfilters as $LPHOST.

-iindent
A numeric option passed by lpd; can be set by the user by the -i option to lpr. Although
nominally used for the amount of indentation requested, magicfilter makes it available to
subfilters for any useful purpose as $LPINDENT.

-Cclassname
LPRng class (priority) name. Available to subfilters as $LPCLASS.

-Fformat
Format letter (passed by LPRng only). When used as input filter (if) this will be f, when used as
other filter types it will be the option character corresponding to this filter. Available to
subfilters as $LPFORMAT.

-Jjobname
The name of the printer job (passed by LPRng only). Available to subfilters as $LPJOB.

-Kcopies
Copy count (passed by LPRng only). Available to subfilters as $LPCOPIES.

-Lbannername
User name from the banner page (passed by LPRng only). Available to subfilters as $BANNERNAME.

-Pprinter
Printer name (passed by LPRng only). Available to subfilters as $PRINTER.

-Qqueuename
Spool queue name (passed by LPRng only). Available to subfilters as $LPQUEUE.

-Raccountinfo
Accounting information (passed by LPRng only). Available to subfilters as $LPACCT.

-Zoptions
LPRng ``Z-options''. The LPRng lpr program supports a -Z option, which can be used to pass
arbitrary information to the printer filters. Available to subfilters as $ZOPT.

--debug
Write the name of each facility invoked (together with any options) to standard error. This can
be useful for debugging complicated configuration files.

other options
Any other options, such as the -w, -l, -x, and -y options typically passed by lpd are ignored.

RUNNING MAGICFILTER FROM LPD
To run magicfilter from lpd it should be entered as one of the filters in the /etc/printcap file.
Typically, it will be the input filter (if). Since most version of lpd do not accept arguments entered
as part of the filter name, typically the filter name entered into the /etc/printcap file will simply be
the name of the configuration file, which is set executable and starts with the line:

#! /usr/sbin/magicfilter

Most UNIX kernels will then be able to treat the configuration file itself as if it was the actual
program.

For systems which do not support the ``#!-hack'', the filter set in the if entry should point to
magicfilter directly, and the accounting file (af) entry should point to the configuration file. This,
however, is a less general, and hence less desirable solution.

This version of magicfilter supports the enhanced lpd included with the LPRng package from
dickory.sdsu.edu.

THE CONFIGURATION FILE
The configuration file is used by magicfilter to redirect various types of data to the various conversion
utilities. The configuration file is printer-specific, and often system-specific, depending on the
available conversion programs. For example, a system which has GhostScript installed would be able to
print PostScript to a non-PostScript printer, whereas other systems typically would not.

The configuration file contains a sequence of lines of the form:

offset magic facility

where the offset represents the location of the indentification string in the data format, magic
represents the identification string itself, facility represents the type of action to take.

Blank lines and lines with a hash mark (#) as the first nonblank character are ignored. A line may be
continued onto the next line by ending the line in a backslash (\).

The offset is a nonnegative integer, which can be represented either in decimal form (default), octal
form (preceded by 0), or hexadecimal form (preceded by 0x).

The magic is a string of characters, which may include C-style \-escape sequences. In addition, the
sequence \? can be used to represent a ``wildcard'' byte. If the string includes spaces, the spaces have
to be preceded by a backslash, or the entire string must be enclosed in double quotation marks.

For ambiguous matches, the first match is used. Hence, the most specific match should always be placed
first in the file. In addition, the last line may be of the form:

default facility

which designates a default action to be used in case no other action matches. This will typically be the
action for plain text.

FACILITIES
magicfilter provides the following options for the facility field in the configuration file:

cat [prefix [suffix]]
Copy the input to the output without any conversion, like the cat command. If the optional prefix
and suffix strings are specified, they are transmitted to the printer immediately before and after
the data itself. The prefix and suffix strings are specified in the same way as the magic string
(except that the wildcard sequence \? is not permitted), and like the magic sequence can contain
any control character, including nulls (\0). To specify a suffix without a prefix, specify an
empty prefix string enclosed in double quotes (i.e. "").

text [prefix [suffix]]
Copy the input to the output, but add carriage return characters before every line feed and form
feed character in the file, and a line feed-form feed sequence at end of file. The prefix and
suffix arguments are treated the same way as for the cat facility; the suffix, if present, is
added after the final line feed-form feed sequence.

postscript
Same as the text facility, except add an ASCII EOT (Ctrl-D) character to the end of the data.
This lets a PostScript printer know that the end of the job has been reached. This is
functionally equivalent to the command

text "" \004

ignore Ignore the job; do not provide any output whatsoever.

reject message
Same as the ignore facility, but attempt to send an email message to the user who submitted the
job to inform that a job has been rejected and why.

filter command
Run the given command, feeding it the input data, and sending the output data to the printer. The
environment variables LPUSER, LPHOST, and LPINDENT is set to the values of the user, host and
indent options passed to magicfilter. Since the command is fed to /bin/sh it may contain shell
special characters, and the sequences $LPUSER, $LPHOST, and $LPINDENT can be used to access the
values of the passed environment variables. If the lpd daemon on the system is LPRng, the
following environment variables are also available, see the OPTIONS section for details: LPCLASS,
LPFORMAT, LPJOB, LPCOPIES, BANNERNAME, PRINTER, LPQUEUE, LPACCT, and ZOPT.

pipe command
Same as the filter facility, except that the output data is fed back into magicfilter for
reprocessing. This is used for external filter programs which themselves do not produce a format
that the printer can accept, but which can be futher processed to obtain such a format.

ffilter command

fpipe command
Same as the filter and pipe facilities, respectively, except that the input is written to a
temporary file before being fed to the filter program given by command. This is useful for
programs which require seekable input, such as dvips, or which need to do multiple passes over an
input file, such as grog. The environment variable FILE is set to the name of the temporary file
(and, like the other ones, it can be accessed on the command line as $FILE).

HINTS

       Using the pipe facility together with zcat or gunzip lets you transparently print compressed files.

       The  pbmplus  or  netpbm  collections of image conversion utilities contain a large number of very useful
       external filter programs.

       You will probably  want  to  examine  the  sample  configuration  files  included  with  the  magicfilter
       distribution before creating your own.

BUGS

       Some data formats cannot be easily identified by a simple fixed-offset magic number check.

       Providing  large offsets can cause magicfilter to take up lots of memory.  Fortunately, large offsets for
       magic numbers are pretty much unheard of.

       Currently, there is no protection against the pipe or fpipe facilities going into an infinite loop.

AUTHOR