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 2007-2008 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
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  13 .\"   file is missing or damaged, see the license at "http://www.cups.org/".
  14 .\"
  15 .TH backend 7 "Common UNIX Printing System" "28 July 2008" "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     device-class device-uri "device-make-and-model" "device-info" "device-id" "device-location"
  63 .fi
  64
  65 .LP
  66 The \fIdevice-class\fR field is one of the following values:
  67
  68 .TP 5
  69 direct
  70 .br
  71 The device-uri refers to a specific direct-access device with no
  72 options, such as a parallel, USB, or SCSI device.
  73
  74 .TP 5
  75 file
  76 .br
  77 The device-uri refers to a file on disk.
  78
  79 .TP 5
  80 network
  81 .br
  82 The device-uri refers to a networked device and conforms to the
  83 general form for network URIs.
  84
  85 .TP 5
  86 serial
  87 .br
  88 The device-uri refers to a serial device with configurable baud
  89 rate and other options. If the device-uri contains a baud value,
  90 it represents the maximum baud rate supported by the device.
  91
  92 .LP
  93 The \fIscheme\fR field provides the URI scheme that is supported
  94 by the backend. Backends should use this form only when the
  95 backend supports any URI using that scheme. The \fIdevice-uri\fR
  96 field specifies the full URI to use when communicating with the
  97 device.
  98
  99 .LP
 100 The \fIdevice-make-and-model\fR field specifies the make and
 101 model of the device, e.g. "Acme Foojet 2000". If the make and
 102 model is not known, you must report "Unknown".
 103
 104 .LP
 105 The \fIdevice-info\fR field specifies additional information
 106 about the device. Typically this includes the make and model
 107 along with the port number or network address, e.g. "Acme Foojet
 108 2000 USB #1".
 109
 110 .LP
 111 The optional \fIdevice-id\fR field specifies the IEEE-1284 device
 112 ID string for the device, which is used to select a matching
 113 driver.
 114
 115 .LP
 116 The optional \fIdevice-location\fR field specifies the physical location of
 117 the device, which is often used to pre-populate the printer-location attribute
 118 when adding a printer.
 119
 120 .SH PERMISSIONS
 121 Backends without world execute permissions are run as the root
 122 user. Otherwise, the backend is run using the unprivileged user
 123 account, typically "lp".
 124
 125 .SH EXIT CODES
 126 The following exit codes are defined for backends; C API
 127 constants defined in the <cups/backend.h> header file are defined
 128 in parenthesis:
 129
 130 .TP 5
 131 0 (CUPS_BACKEND_OK)
 132 .br
 133 The print file was successfully transmitted to the device or
 134 remote server.
 135
 136 .TP 5
 137 1 (CUPS_BACKEND_FAILED)
 138 .br
 139 The print file was not successfully transmitted to the device or
 140 remote server. The scheduler will respond to this by canceling
 141 the job, retrying the job, or stopping the queue depending on the
 142 state of the error-policy attribute.
 143
 144 .TP 5
 145 2 (CUPS_BACKEND_AUTH_REQUIRED)
 146 .br
 147 The print file was not successfully transmitted because valid
 148 authentication information is required. The scheduler will
 149 respond to this by holding the job and adding the
 150 authentication-required job-reasons keyword.
 151
 152 .TP 5
 153 3 (CUPS_BACKEND_HOLD)
 154 .br
 155 The print file was not successfully transmitted because it cannot
 156 be printed at this time. The scheduler will respond to this by
 157 holding the job.
 158
 159 .TP 5
 160 4 (CUPS_BACKEND_STOP)
 161 .br
 162 The print file was not successfully transmitted because it cannot
 163 be printed at this time. The scheduler will respond to this by
 164 stopping the queue.
 165
 166 .TP 5
 167 5 (CUPS_BACKEND_CANCEL)
 168 .br
 169 The print file was not successfully transmitted because one or
 170 more attributes are not supported. The scheduler will respond to
 171 this by canceling the job.
 172
 173 .PP
 174 All other exit code values are reserved.
 175
 176 .SH SEE ALSO
 177 \fIcupsd(8)\fR, \fIcupsd.conf(5)\fR, \fIfilter(7)\fR
 178 .br
 179 http://localhost:631/help
 180
 181 .SH COPYRIGHT
 182 Copyright 2007-2008 by Apple Inc.
 183 .\"
 184 .\" End of "$Id: backend.man 7600 2008-05-20 21:06:23Z mike $".
 185 .\"