backend(7)

1backend(7)                        Apple Inc.                        backend(7)
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NAME

6       backend - cups backend transmission interfaces
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SYNOPSIS

10       backend
11       backend job user title num-copies options [ filename ]
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DESCRIPTION

15       Backends  are  a  special type of filter(7) which is used to send print
16       data to and discover different devices on the system.
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19       Like filters, backends must be capable of reading from  a  filename  on
20       the command-line or from the standard input, copying the standard input
21       to a temporary file as required by the physical interface.
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24       The command name (argv[0]) is set to the device URI of the  destination
25       printer.   Starting with CUPS 1.1.22, any authentication information in
26       argv[0] is  removed,  so  backend  developers  are  urged  to  use  the
27       DEVICE_URI  environment variable whenever authentication information is
28       required. The CUPS API includes  a  cupsBackendDeviceURI  function  for
29       retrieving the correct device URI.
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32       Back-channel  data from the device should be relayed to the job filters
33       by writing to file descriptor  3.  The  CUPS  API  includes  the  cups‐
34       BackChannelWrite function for this purpose.
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DEVICE DISCOVERY

38       When  run  with  no  arguments, the backend should list the devices and
39       schemes it supports or is advertising to stdout. The output consists of
40       zero or more lines consisting of any of the following forms:
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42           device-class scheme "Unknown" "device-info"
43           device-class device-uri "device-make-and-model" "device-info"
44           device-class device-uri "device-make-and-model" "device-info" "device-id"
45           device-class device-uri "device-make-and-model" "device-info" "device-id" "device-location"
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48       The device-class field is one of the following values:
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51       direct
52            The  device-uri  refers to a specific direct-access device with no
53            options, such as a parallel, USB, or SCSI device.
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56       file
57            The device-uri refers to a file on disk.
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60       network
61            The device-uri refers to a networked device and  conforms  to  the
62            general form for network URIs.
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65       serial
66            The  device-uri  refers  to a serial device with configurable baud
67            rate and other options. If the device-uri contains a  baud  value,
68            it represents the maximum baud rate supported by the device.
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71       The scheme field provides the URI scheme that is supported by the back‐
72       end. Backends should use this form only when the backend  supports  any
73       URI  using  that scheme. The device-uri field specifies the full URI to
74       use when communicating with the device.
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77       The device-make-and-model field specifies the make  and  model  of  the
78       device,  e.g.  "Acme  Foojet 2000". If the make and model is not known,
79       you must report "Unknown".
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82       The  device-info  field  specifies  additional  information  about  the
83       device.  Typically this includes the make and model along with the port
84       number or network address, e.g. "Acme Foojet 2000 USB #1".
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87       The optional device-id field specifies the IEEE-1284 device  ID  string
88       for the device, which is used to select a matching driver.
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91       The  optional  device-location field specifies the physical location of
92       the device, which is often used to  pre-populate  the  printer-location
93       attribute when adding a printer.
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PERMISSIONS

97       Backends  without  world  execute permissions are run as the root user.
98       Otherwise, the backend is run using the unprivileged user account, typ‐
99       ically "lp".
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EXIT CODES

103       The  following  exit  codes  are  defined for backends; C API constants
104       defined in the <cups/backend.h> header file are defined in parenthesis:
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107       0 (CUPS_BACKEND_OK)
108            The print file was  successfully  transmitted  to  the  device  or
109            remote server.
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112       1 (CUPS_BACKEND_FAILED)
113            The  print  file was not successfully transmitted to the device or
114            remote server. The scheduler will respond to this by canceling the
115            job,  retrying  the  job,  or  stopping the queue depending on the
116            state of the error-policy attribute.
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119       2 (CUPS_BACKEND_AUTH_REQUIRED)
120            The print file was  not  successfully  transmitted  because  valid
121            authentication information is required. The scheduler will respond
122            to this by holding the job and adding the  authentication-required
123            job-reasons keyword.
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126       3 (CUPS_BACKEND_HOLD)
127            The  print file was not successfully transmitted because it cannot
128            be printed at this time. The scheduler will  respond  to  this  by
129            holding the job.
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132       4 (CUPS_BACKEND_STOP)
133            The  print file was not successfully transmitted because it cannot
134            be printed at this time. The scheduler will  respond  to  this  by
135            stopping the queue.
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138       5 (CUPS_BACKEND_CANCEL)
139            The  print  file  was  not successfully transmitted because one or
140            more attributes are not supported. The scheduler will  respond  to
141            this by canceling the job.
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144       All other exit code values are reserved.
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COPYRIGHT

153       Copyright 2007-2009 by Apple Inc.
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15712 May 2009                          CUPS                           backend(7)