.\"
-.\" "$Id: backend.man 7810 2008-07-29 01:11:15Z mike $"
+.\" "$Id: backend.man 11022 2013-06-06 22:14:09Z msweet $"
.\"
-.\" Backend man page for the Common UNIX Printing System (CUPS).
+.\" Backend man page for CUPS.
.\"
-.\" Copyright 2007-2009 by Apple Inc.
+.\" Copyright 2007-2013 by Apple Inc.
.\" Copyright 1997-2006 by Easy Software Products.
.\"
.\" These coded instructions, statements, and computer programs are the
.\" which should have been included with this file. If this file is
.\" file is missing or damaged, see the license at "http://www.cups.org/".
.\"
-.TH backend 7 "Common UNIX Printing System" "28 July 2008" "Apple Inc."
+.TH backend 7 "CUPS" "23 April 2012" "Apple Inc."
.SH NAME
backend \- cups backend transmission interfaces
-
.SH SYNOPSIS
.B backend
.br
job user title num-copies options [
.I filename
]
-
.SH DESCRIPTION
-Backends are a special type of \fIfilter(7)\fR which is used to
-send print data to and discover different devices on the system.
-
+Backends are a special type of \fIfilter(7)\fR which is used to send print data
+to and discover different devices on the system.
.LP
-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.
-
+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.
.LP
-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 \fIcupsBackendDeviceURI\fR function for
-retrieving the correct device URI.
-
+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
+\fIcupsBackendDeviceURI\fR function for retrieving the correct device URI.
.LP
Back-channel data from the device should be relayed to the job
filters by writing to file descriptor 3. The CUPS API includes
the \fIcupsBackChannelWrite\fR function for this purpose.
-
+.SH WARNING
+CUPS backends are not generally design to be run directly by the user. Aside
+from the device URI issue (argv[0] and DEVICE_URI environment variable contain
+the device URI), CUPS backends also expect specific environment variables and
+file descriptors, and typically run in a user session that (on OS X) has
+additional restrictions that affect how it runs. Backends can also be installed
+with restricted permissions (0500 or 0700) that tell the scheduler to run them
+as the "root" user instead of an unprivileged user (typically "lp") on the
+system.
+.LP
+Unless you are a developer and know what you are doing, please do not run
+backends directly. Instead, use the \fIlp(1)\fR or \fIlpr(1)\fR programs to send
+a print job or \fIlpinfo(8)\fR program to query for available printers using the
+backend. The one exception is the SNMP backend - see \fIsnmpbackend(8)\fR for
+more information.
.SH 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:
+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:
.nf
device-class scheme "Unknown" "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"
.fi
-
.LP
The \fIdevice-class\fR field is one of the following values:
-
.TP 5
direct
.br
-The device-uri refers to a specific direct-access device with no
-options, such as a parallel, USB, or SCSI device.
-
+The device-uri refers to a specific direct-access device with no options, such
+as a parallel, USB, or SCSI device.
.TP 5
file
.br
The device-uri refers to a file on disk.
-
.TP 5
network
.br
-The device-uri refers to a networked device and conforms to the
-general form for network URIs.
-
+The device-uri refers to a networked device and conforms to the general form for
+network URIs.
.TP 5
serial
.br
-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 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.
.LP
-The \fIscheme\fR 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 \fIdevice-uri\fR
-field specifies the full URI to use when communicating with the
-device.
-
+The \fIscheme\fR 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 \fIdevice-uri\fR field specifies the full URI to use when
+communicating with the device.
.LP
-The \fIdevice-make-and-model\fR 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 \fIdevice-make-and-model\fR field specifies the make and model of the
+device, e.g. "Example Foojet 2000". If the make and model is not known, you must
+report "Unknown".
.LP
-The \fIdevice-info\fR 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 \fIdevice-info\fR field specifies additional information about the device.
+Typically this includes the make and model along with the port number or network
+address, e.g. "Example Foojet 2000 USB #1".
.LP
-The optional \fIdevice-id\fR field specifies the IEEE-1284 device
-ID string for the device, which is used to select a matching
-driver.
-
+The optional \fIdevice-id\fR field specifies the IEEE-1284 device ID string for
+the device, which is used to select a matching driver.
.LP
The optional \fIdevice-location\fR field specifies the physical location of
the device, which is often used to pre-populate the printer-location attribute
when adding a printer.
-
.SH PERMISSIONS
-Backends without world execute permissions are run as the root
-user. Otherwise, the backend is run using the unprivileged user
-account, typically "lp".
-
+Backends without world execute permissions are run as the root user. Otherwise,
+the backend is run using an unprivileged user account, typically "lp".
.SH 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:
-
+The following exit codes are defined for backends; C API constants defined in
+the <cups/backend.h> header file are defined in parenthesis:
.TP 5
0 (CUPS_BACKEND_OK)
.br
-The print file was successfully transmitted to the device or
-remote server.
-
+The print file was successfully transmitted to the device or remote server.
.TP 5
1 (CUPS_BACKEND_FAILED)
.br
-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.
-
+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.
.TP 5
2 (CUPS_BACKEND_AUTH_REQUIRED)
.br
-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.
-
+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 "cups-held-for-authentication" keyword to the "job-reasons"
+attribute.
.TP 5
3 (CUPS_BACKEND_HOLD)
.br
-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.
-
+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.
.TP 5
4 (CUPS_BACKEND_STOP)
.br
-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.
-
+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.
.TP 5
5 (CUPS_BACKEND_CANCEL)
.br
-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.
-
+The print file was not successfully transmitted because one or more attributes
+are not supported or the job was canceled at the printer. The scheduler will
+respond to this by canceling the job.
+.TP 5
+6 (CUPS_BACKEND_RETRY)
+.br
+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.
+.TP 5
+7 (CUPS_BACKEND_RETRY_CURRENT)
+.br
+The print file was not successfully transmitted because of a temporary issue.
+The scheduler will retry the job immediately without allowing intervening jobs.
.PP
All other exit code values are reserved.
-
.SH SEE ALSO
-\fIcupsd(8)\fR, \fIcupsd.conf(5)\fR, \fIfilter(7)\fR
+\fIcups-snmp(8)\fR, \fIcupsd(8)\fR, \fIcupsd.conf(5)\fR, \fIfilter(7)\fR,
+\fIlpinfo(8)\fR,
.br
http://localhost:631/help
-
.SH COPYRIGHT
-Copyright 2007-2009 by Apple Inc.
+Copyright 2007-2013 by Apple Inc.
.\"
-.\" End of "$Id: backend.man 7810 2008-07-29 01:11:15Z mike $".
+.\" End of "$Id: backend.man 11022 2013-06-06 22:14:09Z msweet $".
.\"
projects / thirdparty / cups.git / blobdiff