Provided by: cups_1.5.2-9ubuntu1_amd64 bug

NAME

       backend - cups backend transmission interfaces

SYNOPSIS

       backend
       backend job user title num-copies options [ filename ]

DESCRIPTION

       Backends  are a special type of filter(7) which is used to send print data to and discover
       different devices on the system.

       Like filters, backends must be capable of reading from a filename on the  command-line  or
       from the standard input, copying the standard input to a temporary file as required by the
       physical interface.

       The command name (argv[0]) is set to the device URI of the destination printer.   Starting
       with  CUPS  1.1.22,  any  authentication  information  in  argv[0]  is removed, so backend
       developers are urged to use the DEVICE_URI environment  variable  whenever  authentication
       information  is  required.  The  CUPS  API  includes  a  cupsBackendDeviceURI function for
       retrieving the correct device URI.

       Back-channel data from the device should be relayed to the job filters by writing to  file
       descriptor 3. The CUPS API includes the cupsBackChannelWrite function for this purpose.

DEVICE DISCOVERY

       When run with no arguments, the backend should list the devices and schemes it supports or
       is advertising to stdout. The output consists of zero or more lines consisting of  any  of
       the following forms:

           device-class scheme "Unknown" "device-info"
           device-class device-uri "device-make-and-model" "device-info"
           device-class device-uri "device-make-and-model" "device-info" "device-id"
           device-class device-uri "device-make-and-model" "device-info" "device-id" "device-location"

       The device-class field is one of the following values:

       direct
            The  device-uri  refers to a specific direct-access device with no options, such as a
            parallel, USB, or SCSI device.

       file
            The device-uri refers to a file on disk.

       network
            The device-uri refers to a networked device and conforms  to  the  general  form  for
            network URIs.

       serial
            The  device-uri  refers  to  a  serial  device  with configurable baud rate and other
            options. If the device-uri contains a baud value, it represents the maximum baud rate
            supported by the device.

       The scheme field provides the URI scheme that is supported by the backend. Backends should
       use this form only when the backend supports any URI using  that  scheme.  The  device-uri
       field specifies the full URI to use when communicating with the device.

       The  device-make-and-model  field  specifies  the make and model of the device, e.g. "Acme
       Foojet 2000". If the make and model is not known, you must report "Unknown".

       The device-info field specifies additional information about the  device.  Typically  this
       includes  the  make  and  model  along with the port number or network address, e.g. "Acme
       Foojet 2000 USB #1".

       The optional device-id field specifies the IEEE-1284 device  ID  string  for  the  device,
       which is used to select a matching driver.

       The optional device-location field specifies the physical location of the device, which is
       often used to pre-populate the printer-location attribute when adding a printer.

PERMISSIONS

       Backends without world execute permissions are  run  as  the  root  user.  Otherwise,  the
       backend is run using the unprivileged user account, typically "lp".

EXIT CODES

       The  following  exit  codes  are  defined  for  backends;  C  API constants defined in the
       <cups/backend.h> header file are defined in parenthesis:

       0 (CUPS_BACKEND_OK)
            The print file was successfully transmitted to the device or remote server.

       1 (CUPS_BACKEND_FAILED)
            The print file was not successfully transmitted to the device or remote  server.  The
            scheduler  will  respond  to this by canceling the job, retrying the job, or stopping
            the queue depending on the state of the error-policy attribute.

       2 (CUPS_BACKEND_AUTH_REQUIRED)
            The  print  file  was  not  successfully  transmitted  because  valid  authentication
            information  is  required.  The scheduler will respond to this by holding the job and
            adding the authentication-required job-reasons keyword.

       3 (CUPS_BACKEND_HOLD)
            The print file was not successfully transmitted because it cannot be printed at  this
            time. The scheduler will respond to this by holding the job.

       4 (CUPS_BACKEND_STOP)
            The  print file was not successfully transmitted because it cannot be printed at this
            time. The scheduler will respond to this by stopping the queue.

       5 (CUPS_BACKEND_CANCEL)
            The print file was not successfully transmitted because one or  more  attributes  are
            not supported. The scheduler will respond to this by canceling the job.

       6 (CUPS_BACKEND_RETRY)
            The  print  file  was not successfully transmitted because of a temporary issue.  The
            scheduler will retry the job at a future time - other jobs may print before this one.

       7 (CUPS_BACKEND_RETRY_CURRENT)
            The print file was not successfully transmitted because of a  temporary  issue.   The
            scheduler will retry the job immediately without allowing intervening jobs.

       All other exit code values are reserved.

SEE ALSO

       cupsd(8), cupsd.conf(5), filter(7),
       http://localhost:631/help

COPYRIGHT

       Copyright 2007-2011 by Apple Inc.