backend(7)

1backend(7)                  Easy Software Products                  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"
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47       The device-class field is one of the following values:
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50       direct
51            The  device-uri  refers to a specific direct-access device with no
52            options, such as a parallel, USB, or SCSI device.
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55       file
56            The device-uri refers to a file on disk.
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59       network
60            The device-uri refers to a networked device and  conforms  to  the
61            general form for network URIs.
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64       serial
65            The  device-uri  refers  to a serial device with configurable baud
66            rate and other options. If the device-uri contains a  baud  value,
67            it represents the maximum baud rate supported by the device.
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70       The scheme field provides the URI scheme that is supported by the back‐
71       end. Backends should use this form only when the backend  supports  any
72       URI  using  that scheme. The device-uri field specifies the full URI to
73       use when communicating with the device.
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76       The device-make-and-model field specifies the make  and  model  of  the
77       device,  e.g.  "Acme  Foojet 2000". If the make and model is not known,
78       you must report "Unknown".
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81       The  device-info  field  specifies  additional  information  about  the
82       device.  Typically this includes the make and model along with the port
83       number or network address, e.g. "Acme Foojet 2000 USB #1".
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86       The optional device-id field specifies the IEEE-1284 device  ID  string
87       for the device, which is used to select a matching driver.
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PERMISSIONS

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

97       The  following  exit  codes  are  defined for backends; C API constants
98       defined in the <cups/backend.h> header file are defined in parenthesis:
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101       0 (CUPS_BACKEND_OK)
102            The print file was  successfully  transmitted  to  the  device  or
103            remote server.
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106       1 (CUPS_BACKEND_FAILED)
107            The  print  file was not successfully transmitted to the device or
108            remote server. The scheduler will respond to this by canceling the
109            job,  retrying  the  job,  or  stopping the queue depending on the
110            state of the error-policy attribute.
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113       2 (CUPS_BACKEND_AUTH_REQUIRED)
114            The print file was  not  successfully  transmitted  because  valid
115            authentication information is required. The scheduler will respond
116            to this by holding the job and adding the  authentication-required
117            job-reasons keyword.
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120       3 (CUPS_BACKEND_HOLD)
121            The  print file was not successfully transmitted because it cannot
122            be printed at this time. The scheduler will  respond  to  this  by
123            holding the job.
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126       4 (CUPS_BACKEND_STOP)
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            stopping the queue.
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132       5 (CUPS_BACKEND_CANCEL)
133            The  print  file  was  not successfully transmitted because one or
134            more attributes are not supported. The scheduler will  respond  to
135            this by canceling the job.
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138       All other exit code values are reserved.
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COPYRIGHT

147       Copyright 1997-2006 by Easy Software Products, All Rights Reserved.
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15120 March 2006             Common UNIX Printing System               backend(7)