filter(7) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | OPTIONS | LOG MESSAGES | ENVIRONMENT VARIABLES | CONFORMING TO | NOTES | SEE ALSO | COPYRIGHT | COLOPHON

filter(7)                      Apple Inc.                      filter(7)

NAME         top

       filter - cups file conversion filter interface

SYNOPSIS         top

       filter job user title num-copies options [ filename ]

       #include <cups/cups.h>

       ssize_t cupsBackChannelRead(char *buffer, size_t bytes,
                                   double timeout);

       cups_sc_status_t cupsSideChannelDoRequest(cups_sc_command_t command,
                                                 char *data, int *datalen,
                                                 double timeout);

       #include <cups/ppd.h>

       const char *cupsGetOption(const char *name, int num_options,
                        cups_option_t *options);

       int cupsMarkOptions(ppd_file_t *ppd, int num_options,
                           cups_option_t *options);

       int cupsParseOptions(const char *arg, int num_options,
                            cups_option_t **options);

       ppd_choice_t *ppdFindMarkedChoice(ppd_file_t *ppd, const char *keyword);

       void ppdMarkDefaults(ppd_file_t *ppd);

       ppd_file_t *ppdOpenFile(const char *filename);

DESCRIPTION         top

       The CUPS filter interface provides a standard method for adding
       support for new document types or printers to CUPS.  Each filter
       is capable of converting from one or more input formats to
       another format that can either be printed directly or piped into
       another filter to get it to a printable format.

       Filters 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 file format.  All
       output MUST be sent to the standard output.  Filters MUST NOT
       attempt to communicate directly with the printer, other
       processes, or other services.

       The command name (argv[0]) is set to the name of the destination
       printer but is also available in the PRINTER environment
       variable.

OPTIONS         top

       Options are passed in argv[5] and are encoded from the
       corresponding IPP attributes used when the job was submitted. Use
       the cupsParseOptions() function to load the options into a
       cups_option_t array and the cupsGetOption() function to get the
       value of a specific attribute.  Be careful to look for common
       aliases of IPP attributes such as "landscape" for the IPP
       "orientation-requested" attribute.

       Options passed on the command-line typically do not include the
       default choices the printer's PPD file. Use the ppdMarkDefaults()
       and cupsMarkOptions() functions in the CUPS library to apply the
       options to the PPD defaults and map any IPP attributes to the
       corresponding PPD options.  Use ppdFindMarkedChoice() to get the
       user-selected choice for a PPD option. For example, a filter
       might use the following code to determine the current value of
       the Duplex PPD option:

           ppd_file_t *ppd = ppdOpenFile(getenv("PPD"));
           cups_option_t *options = NULL;
           int num_options = cupsParseOptions(argv[5], 0, &options);

           ppdMarkDefaults(ppd);
           cupsMarkOptions(ppd, num_options, options);

           ppd_choice_t *choice = ppdFindMarkedChoice(ppd, "Duplex");

       Raster filters should use option choices set through the raster
       page header, as those reflect the options in effect for a given
       page.  Options specified on the command-line determine the
       default values for the entire job, which can be overridden on a
       per-page basis.

LOG MESSAGES         top

       Messages sent to the standard error are generally stored in the
       printer's "printer-state-message" attribute and the current
       ErrorLog file.  Each line begins with a standard prefix:

       ALERT: message
            Sets the "printer-state-message" attribute and adds the
            specified message to the current ErrorLog using the "alert"
            log level.

       ATTR: attribute=value [ ... attribute=value]
            Sets the named job or printer attribute(s). The following
            job attributes can be set: "job-media-progress". The
            following printer attributes can be set: "auth-info-
            required", "marker-colors", "marker-high-levels", "marker-
            levels", "marker-low-levels", "marker-message", "marker-
            names", "marker-types", "printer-alert", and "printer-alert-
            description".

       CRIT: message
            Sets the "printer-state-message" attribute and adds the
            specified message to the current ErrorLog using the
            "critical" log level.

       DEBUG: message
            Adds the specified message to the current ErrorLog using the
            "debug" log level.  DEBUG messages are never stored in the
            "printer-state-message" attribute.

       DEBUG2: message
            Adds the specified message to the current ErrorLog using the
            "debug2" log level.  DEBUG2 messages are never stored in the
            "printer-state-message" attribute.

       EMERG: message
            Sets the "printer-state-message" attribute and adds the
            specified message to the current ErrorLog using the
            "emergency" log level.

       ERROR: message
            Sets the "printer-state-message" attribute and adds the
            specified message to the current ErrorLog using the "error"
            log level.

       INFO: message
            Sets the "printer-state-message" attribute. If the current
            LogLevel is set to "debug2", also adds the specified message
            to the current ErrorLog using the "info" log level.

       NOTICE: message
            Sets the "printer-state-message" attribute and adds the
            specified message to the current ErrorLog using the "notice"
            log level.

       PAGE: page-number #-copies

       PAGE: total #-pages
            Adds an entry to the current PageLog. The first form adds
            #-copies to the "job-media-sheets-completed" attribute. The
            second form sets the "job-media-sheets-completed" attribute
            to #-pages.

       PPD: Keyword=Value [ ... KeywordN=Value ]
            Sets the named keywords in the printer's PPD file. This is
            typically used to update default option keywords such as
            DefaultPageSize and the various installable options in the
            PPD file.

       STATE: printer-state-reason [ ... printer-state-reason ]

       STATE: + printer-state-reason [ ... printer-state-reason ]

       STATE: - printer-state-reason [ ... printer-state-reason ]
            Sets, adds, or removes "printer-state-reason" keywords for
            the current queue. Typically this is used to indicate media,
            ink, and toner conditions on a printer.

       WARNING: message
            Sets the "printer-state-message" attribute and adds the
            specified message to the current ErrorLog using the
            "warning" log level.

ENVIRONMENT VARIABLES         top

       The following environment variables are defined by the CUPS
       server when executing the filter:

       CHARSET
            The default text character set, typically "utf-8".

       CLASS
            When a job is submitted to a printer class, contains the
            name of the destination printer class. Otherwise this
            environment variable will not be set.

       CONTENT_TYPE
            The MIME media type associated with the submitted job file,
            for example "application/postscript".

       CUPS_CACHEDIR
            The directory where semi-persistent cache files can be found
            and stored.

       CUPS_DATADIR
            The directory where data files can be found.

       CUPS_FILETYPE
            The type of file being printed: "job-sheet" for a banner
            page and "document" for a regular print file.

       CUPS_MAX_MESSAGE
            The maximum size of a message sent to stderr, including any
            leading prefix and the trailing newline.

       CUPS_SERVERROOT
            The root directory of the server.

       FINAL_CONTENT_TYPE
            The MIME media type associated with the output destined for
            the printer, for example "application/vnd.cups-postscript".

       LANG The default language locale (typically C or en).

       PATH The standard execution path for external programs that may
            be run by the filter.

       PPD  The full pathname of the PostScript Printer Description
            (PPD) file for this printer.

       PRINTER
            The name of the printer.

       RIP_CACHE
            The recommended amount of memory to use for Raster Image
            Processors (RIPs).

       SOFTWARE
            The name and version number of the server (typically
            CUPS/major.minor).

       TZ   The timezone of the server.

       USER The user executing the filter, typically "lp" or "root";
            consult the cups-files.conf file for the current setting.

CONFORMING TO         top

       While the filter interface is compatible with System V interface
       scripts, CUPS does not support System V interface scripts.

NOTES         top

       CUPS printer drivers and backends are deprecated and will no
       longer be supported in a future feature release of CUPS.
       Printers that do not support IPP can be supported using
       applications such as ippeveprinter(1).

       CUPS filters are not meant to be run directly by the user.  Aside
       from the legacy System V interface issues (argv[0] is the printer
       name), CUPS filters also expect specific environment variables
       and file descriptors, and typically run in a user session that
       (on macOS) has additional restrictions that affect how it runs.
       Unless you are a developer and know what you are doing, please do
       not run filters directly.  Instead, use the cupsfilter(8) program
       to use the appropriate filters to do the conversions you need.

SEE ALSO         top

       backend(7), cups(1), cups-files.conf(5), cupsd(8), cupsfilter(8),
       CUPS Online Help (http://localhost:631/help)

COPYRIGHT         top

       Copyright © 2007-2019 by Apple Inc.

COLOPHON         top

       This page is part of the CUPS (a standards-based, open source
       printing system) project.  Information about the project can be
       found at ⟨http://www.cups.org/⟩.  If you have a bug report for
       this manual page, see ⟨http://www.cups.org/⟩.  This page was
       obtained from the project's upstream Git repository
       ⟨https://github.com/apple/cups⟩ on 2021-08-27.  (At that time,
       the date of the most recent commit that was found in the
       repository was 2021-08-24.)  If you discover any rendering
       problems in this HTML version of the page, or you believe there
       is a better or more up-to-date source for the page, or you have
       corrections or improvements to the information in this COLOPHON
       (which is not part of the original manual page), send a mail to
       man-pages@man7.org

26 April 2019                     CUPS                         filter(7)

Pages that refer to this page: backend(7)notifier(7)cupsd(8)cupsd-helper(8)cupsfilter(8)