man/backend.man

   1 .\"
   2 .\" "$Id: backend.man 7600 2008-05-20 21:06:23Z mike $"
   3 .\"
   4 .\"   Backend man page for the Common UNIX Printing System (CUPS).
   5 .\"
   6 .\"   Copyright 2007 by Apple Inc.
   7 .\"   Copyright 1997-2006 by Easy Software Products.
   8 .\"
   9 .\"   These coded instructions, statements, and computer programs are the
  10 .\"   property of Apple Inc. and are protected by Federal copyright
  11 .\"   law.  Distribution and use rights are outlined in the file "LICENSE.txt"
  12 .\"   which should have been included with this file.  If this file is
  13 .\"   file is missing or damaged, see the license at "http://www.cups.org/".
  14 .\"
  15 .TH backend 7 "Common UNIX Printing System" "20 March 2006" "Apple Inc."
  16
  17 .SH NAME
  18 backend \- cups backend transmission interfaces
  19
  20 .SH SYNOPSIS
  21 .B backend
  22 .br
  23 .B backend
  24 job user title num-copies options [
  25 .I filename
  26 ]
  27
  28 .SH DESCRIPTION
  29 Backends are a special type of \fIfilter(7)\fR which is used to
  30 send print data to and discover different devices on the system.
  31
  32 .LP
  33 Like filters, backends must be capable of reading from a filename
  34 on the command-line or from the standard input, copying the
  35 standard input to a temporary file as required by the physical
  36 interface.
  37
  38 .LP
  39 The command name (argv[0]) is set to the device URI of the
  40 destination printer. Starting with CUPS 1.1.22, any
  41 authentication information in argv[0] is removed, so
  42 backend developers are urged to use the DEVICE_URI environment
  43 variable whenever authentication information is required. The
  44 CUPS API includes a \fIcupsBackendDeviceURI\fR function for
  45 retrieving the correct device URI.
  46
  47 .LP
  48 Back-channel data from the device should be relayed to the job
  49 filters by writing to file descriptor 3. The CUPS API includes
  50 the \fIcupsBackChannelWrite\fR function for this purpose.
  51
  52 .SH DEVICE DISCOVERY
  53 When run with no arguments, the backend should list the devices
  54 and schemes it supports or is advertising to stdout. The output
  55 consists of zero or more lines consisting of any of the following
  56 forms:
  57
  58 .nf
  59     device-class scheme "Unknown" "device-info"
  60     device-class device-uri "device-make-and-model" "device-info"
  61     device-class device-uri "device-make-and-model" "device-info" "device-id"
  62 .fi
  63
  64 .LP
  65 The \fIdevice-class\fR field is one of the following values:
  66
  67 .TP 5
  68 direct
  69 .br
  70 The device-uri refers to a specific direct-access device with no
  71 options, such as a parallel, USB, or SCSI device.
  72
  73 .TP 5
  74 file
  75 .br
  76 The device-uri refers to a file on disk.
  77
  78 .TP 5
  79 network
  80 .br
  81 The device-uri refers to a networked device and conforms to the
  82 general form for network URIs.
  83
  84 .TP 5
  85 serial
  86 .br
  87 The device-uri refers to a serial device with configurable baud
  88 rate and other options. If the device-uri contains a baud value,
  89 it represents the maximum baud rate supported by the device.
  90
  91 .LP
  92 The \fIscheme\fR field provides the URI scheme that is supported
  93 by the backend. Backends should use this form only when the
  94 backend supports any URI using that scheme. The \fIdevice-uri\fR
  95 field specifies the full URI to use when communicating with the
  96 device.
  97
  98 .LP
  99 The \fIdevice-make-and-model\fR field specifies the make and
 100 model of the device, e.g. "Acme Foojet 2000". If the make and
 101 model is not known, you must report "Unknown".
 102
 103 .LP
 104 The \fIdevice-info\fR field specifies additional information
 105 about the device. Typically this includes the make and model
 106 along with the port number or network address, e.g. "Acme Foojet
 107 2000 USB #1".
 108
 109 .LP
 110 The optional \fIdevice-id\fR field specifies the IEEE-1284 device
 111 ID string for the device, which is used to select a matching
 112 driver.
 113
 114 .SH PERMISSIONS
 115 Backends without world execute permissions are run as the root
 116 user. Otherwise, the backend is run using the unprivileged user
 117 account, typically "lp".
 118
 119 .SH EXIT CODES
 120 The following exit codes are defined for backends; C API
 121 constants defined in the <cups/backend.h> header file are defined
 122 in parenthesis:
 123
 124 .TP 5
 125 0 (CUPS_BACKEND_OK)
 126 .br
 127 The print file was successfully transmitted to the device or
 128 remote server.
 129
 130 .TP 5
 131 1 (CUPS_BACKEND_FAILED)
 132 .br
 133 The print file was not successfully transmitted to the device or
 134 remote server. The scheduler will respond to this by canceling
 135 the job, retrying the job, or stopping the queue depending on the
 136 state of the error-policy attribute.
 137
 138 .TP 5
 139 2 (CUPS_BACKEND_AUTH_REQUIRED)
 140 .br
 141 The print file was not successfully transmitted because valid
 142 authentication information is required. The scheduler will
 143 respond to this by holding the job and adding the
 144 authentication-required job-reasons keyword.
 145
 146 .TP 5
 147 3 (CUPS_BACKEND_HOLD)
 148 .br
 149 The print file was not successfully transmitted because it cannot
 150 be printed at this time. The scheduler will respond to this by
 151 holding the job.
 152
 153 .TP 5
 154 4 (CUPS_BACKEND_STOP)
 155 .br
 156 The print file was not successfully transmitted because it cannot
 157 be printed at this time. The scheduler will respond to this by
 158 stopping the queue.
 159
 160 .TP 5
 161 5 (CUPS_BACKEND_CANCEL)
 162 .br
 163 The print file was not successfully transmitted because one or
 164 more attributes are not supported. The scheduler will respond to
 165 this by canceling the job.
 166
 167 .PP
 168 All other exit code values are reserved.
 169
 170 .SH SEE ALSO
 171 \fIcupsd(8)\fR, \fIcupsd.conf(5)\fR, \fIfilter(7)\fR
 172 .br
 173 http://localhost:631/help
 174
 175 .SH COPYRIGHT
 176 Copyright 2007 by Apple Inc.
 177 .\"
 178 .\" End of "$Id: backend.man 7600 2008-05-20 21:06:23Z mike $".
 179 .\"