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 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 © 2007-2017 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
       2017-03-13.  If you discover any rendering problems in this HTML ver‐
       sion 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 man‐
       ual page), send a mail to man-pages@man7.org

19 October 2015                     CUPS                           filter(7)