pipe

#! /bin/bash
# CUPS wrapper backend "pipe" for printing to any program.
# It forwards the print job data like a pipe into another command.
# Author: Johannes Meixner <jsmeix@suse.de>, 2009, 2014
# For basic information see "man 7 backend" and "man 7 filter".
# This program is free software; you can redistribute it and/or modify it
# under the terms of the GNU GENERAL PUBLIC LICENSE Version 2
# as published by the Free Software Foundation.

# Activate the "set -x" line to get debugging info in /var/log/cups/error_log:
set -x

# Output "Device Discovery" information on stdout:
if test "$#" = "0"
then
  echo 'direct pipe "Unknown" "Forward print job data like a pipe to another command"'
  exit 0
fi

# Output usage information in case of wrong number of parameters:
if test "$#" != "5" -a "$#" != "6"
then
  echo 'Usage: pipe job-id user title copies options [file]' 1>&2
  echo 'Queue setup example:' 1>&2
  echo 'lpadmin -p queue_name -v "pipe:/path/to/command?option1=value1&-option2&value2" -E' 1>&2
  echo 'The command is called with the specified options as:' 1>&2
  echo '/path/to/command option1=value1 -option2 value2' 1>&2
  echo 'The original command line parameters (... job-id user ...)' 1>&2
  echo 'are provided as environment variables PIPE_BACKEND_ARGV[0-6]' 1>&2
  exit 1
fi

# Keep the original command line parameters (... job-id user ...)
# in environment variables to make them available for the command:
export PIPE_BACKEND_ARGV0="$0"
export PIPE_BACKEND_ARGV1="$1"
export PIPE_BACKEND_ARGV2="$2"
export PIPE_BACKEND_ARGV3="$3"
export PIPE_BACKEND_ARGV4="$4"
export PIPE_BACKEND_ARGV5="$5"
export PIPE_BACKEND_ARGV6="$6"

# Have the input at fd0 (stdin) in any case:
if test -n "$6"
then
  exec <"$6"
fi

# To be on the safe side clip anything after the first space character
# because spaces are excluded characters in a URI (see RFC 2396):
URI=${DEVICE_URI%% *}
# Extract the command to which the job schould be sent from the URI.
# Clip the URI scheme (anything up to the first ':' character) and
# clip anything after the first '?' character
# because anything after the first '?' character are options:
COMMAND=${URI#*:}
COMMAND=${COMMAND%%\?*}
# Extract the options (e.g. from 'pipe:/path/to/command?option1=value1&-option2&value2'
# clip anything up to the first '?' character and
# replace the options separator '&' character by a space:
OPTIONS=${URI#*\?}
if test "$OPTIONS" = "$URI"
then
  OPTIONS=""
fi
OPTIONS=$( echo "$OPTIONS" | tr '&' ' ' )
# Options could have been specified in a wrong way
# as addendum to the DeviceURI separated by spaces
# (spaces are excluded characters in a URI, see RFC 2396)
# which works by luck at least for some CUPS versions
# see https://bugzilla.novell.com/show_bug.cgi?id=499735
# like 'pipe:/path/to/command option1=value1 -option2 value2'
# nevertheless use additionally those kind of options too:
MORE_OPTIONS=${DEVICE_URI#* }
if test "$MORE_OPTIONS" = "$DEVICE_URI"
then
  MORE_OPTIONS=""
fi
OPTIONS=$( echo "$OPTIONS" "$MORE_OPTIONS" | tr -s ' ' )

# Test if the command is executable:
if ! test -x "$COMMAND"
then
  echo "Cannot execute $COMMAND" 1>&2
  exit 1
fi

# Replace this wrapper with the actual command
# so that it exits with the exit code of the command
# and that the command gets any signals directly.
exec "$COMMAND" $OPTIONS