man/backend.man

   1 .\"
   2 .\" "$Id: backend.man 7810 2008-07-29 01:11:15Z mike $"
   3 .\"
   4 .\"   Backend man page for the Common UNIX Printing System (CUPS).
   5 .\"
   6 .\"   Copyright 2007-2009 by Apple Inc.
   7 .\"   Copyright 1997-2006 by Easy Software Products.
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   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/".
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  15 .TH backend 7 "CUPS" "12 May 2009" "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 destination printer.
  40 Starting with CUPS 1.1.22, any authentication information in argv[0] is removed,
  41 so backend developers are urged to use the DEVICE_URI environment variable
  42 whenever authentication information is required. The CUPS API includes a
  43 \fIcupsBackendDeviceURI\fR function for retrieving the correct device URI.
  44
  45 .LP
  46 Back-channel data from the device should be relayed to the job
  47 filters by writing to file descriptor 3. The CUPS API includes
  48 the \fIcupsBackChannelWrite\fR function for this purpose.
  49
  50 .SH DEVICE DISCOVERY
  51 When run with no arguments, the backend should list the devices
  52 and schemes it supports or is advertising to stdout. The output
  53 consists of zero or more lines consisting of any of the following
  54 forms:
  55
  56 .nf
  57     device-class scheme "Unknown" "device-info"
  58     device-class device-uri "device-make-and-model" "device-info"
  59     device-class device-uri "device-make-and-model" "device-info" "device-id"
  60     device-class device-uri "device-make-and-model" "device-info" "device-id" "device-location"
  61 .fi
  62
  63 .LP
  64 The \fIdevice-class\fR field is one of the following values:
  65
  66 .TP 5
  67 direct
  68 .br
  69 The device-uri refers to a specific direct-access device with no
  70 options, such as a parallel, USB, or SCSI device.
  71
  72 .TP 5
  73 file
  74 .br
  75 The device-uri refers to a file on disk.
  76
  77 .TP 5
  78 network
  79 .br
  80 The device-uri refers to a networked device and conforms to the
  81 general form for network URIs.
  82
  83 .TP 5
  84 serial
  85 .br
  86 The device-uri refers to a serial device with configurable baud
  87 rate and other options. If the device-uri contains a baud value,
  88 it represents the maximum baud rate supported by the device.
  89
  90 .LP
  91 The \fIscheme\fR field provides the URI scheme that is supported
  92 by the backend. Backends should use this form only when the
  93 backend supports any URI using that scheme. The \fIdevice-uri\fR
  94 field specifies the full URI to use when communicating with the
  95 device.
  96
  97 .LP
  98 The \fIdevice-make-and-model\fR field specifies the make and
  99 model of the device, e.g. "Acme Foojet 2000". If the make and
 100 model is not known, you must report "Unknown".
 101
 102 .LP
 103 The \fIdevice-info\fR field specifies additional information
 104 about the device. Typically this includes the make and model
 105 along with the port number or network address, e.g. "Acme Foojet
 106 2000 USB #1".
 107
 108 .LP
 109 The optional \fIdevice-id\fR field specifies the IEEE-1284 device
 110 ID string for the device, which is used to select a matching
 111 driver.
 112
 113 .LP
 114 The optional \fIdevice-location\fR field specifies the physical location of
 115 the device, which is often used to pre-populate the printer-location attribute
 116 when adding a printer.
 117
 118 .SH PERMISSIONS
 119 Backends without world execute permissions are run as the root
 120 user. Otherwise, the backend is run using the unprivileged user
 121 account, typically "lp".
 122
 123 .SH EXIT CODES
 124 The following exit codes are defined for backends; C API
 125 constants defined in the <cups/backend.h> header file are defined
 126 in parenthesis:
 127
 128 .TP 5
 129 0 (CUPS_BACKEND_OK)
 130 .br
 131 The print file was successfully transmitted to the device or
 132 remote server.
 133
 134 .TP 5
 135 1 (CUPS_BACKEND_FAILED)
 136 .br
 137 The print file was not successfully transmitted to the device or
 138 remote server. The scheduler will respond to this by canceling
 139 the job, retrying the job, or stopping the queue depending on the
 140 state of the error-policy attribute.
 141
 142 .TP 5
 143 2 (CUPS_BACKEND_AUTH_REQUIRED)
 144 .br
 145 The print file was not successfully transmitted because valid
 146 authentication information is required. The scheduler will
 147 respond to this by holding the job and adding the
 148 authentication-required job-reasons keyword.
 149
 150 .TP 5
 151 3 (CUPS_BACKEND_HOLD)
 152 .br
 153 The print file was not successfully transmitted because it cannot
 154 be printed at this time. The scheduler will respond to this by
 155 holding the job.
 156
 157 .TP 5
 158 4 (CUPS_BACKEND_STOP)
 159 .br
 160 The print file was not successfully transmitted because it cannot
 161 be printed at this time. The scheduler will respond to this by
 162 stopping the queue.
 163
 164 .TP 5
 165 5 (CUPS_BACKEND_CANCEL)
 166 .br
 167 The print file was not successfully transmitted because one or
 168 more attributes are not supported. The scheduler will respond to
 169 this by canceling the job.
 170
 171 .PP
 172 All other exit code values are reserved.
 173
 174 .SH SEE ALSO
 175 \fIcupsd(8)\fR, \fIcupsd.conf(5)\fR, \fIfilter(7)\fR,
 176 .br
 177 http://localhost:631/help
 178
 179 .SH COPYRIGHT
 180 Copyright 2007-2009 by Apple Inc.
 181 .\"
 182 .\" End of "$Id: backend.man 7810 2008-07-29 01:11:15Z mike $".
 183 .\"