Using CGI Programs

CUPS has traditionally provided a dynamic web interface through dedicated CGI programs that are executed when users open special directories on the CUPS server. Each CGI performs administration, class, help, job, and printer functions as directed by the user, but the actual programs that are run and functions that are available are limited to those that were originally designed into the scheduler.

Support is now available for CGI programs and specific scripting languages, currently Java, Perl, PHP, and Python. The interpreters for these languages are currently configured at compile time. Future versions may expand the interface to allow for generic support of scripting languages similar to the Apache "AddHandler" directive, but with external programs instead of modules.

Table 1 shows the MIME media types that are reserved for the CGI support in CUPS. The names have been chosen to mirror those used by Apache:

Table 1: CGI MIME Media Types
MIME Media Type | Description
--- | ---
application/x-httpd-cgi | CGI script/program
application/x-httpd-java | Java program
application/x-httpd-perl | Perl script
application/x-httpd-php | PHP script
application/x-httpd-python | Python script

## Configuring the Server

In order to enable the corresponding type, you must create a new /etc/cups/cgi.types file which maps the filename extensions to the appropriate MIME type, for example:

    application/x-httpd-cgi cgi
    application/x-httpd-java class
    application/x-httpd-perl pl
    application/x-httpd-php php
    application/x-httpd-python py

CGI scripts/programs (application/x-httpd-cgi) also must have execution permissions to be treated as a CGI script or program.

## Limitations

CUPS implements most of the CGI/1.1 specification, with the following exceptions:

- No PATH_INFO or PATH_TRANSLATED support
- Limited HTTP field support; only the Content-Length (CONTENT_LENGTH), Cookie (HTTP_COOKIE), and User-Agent (HTTP_USER_AGENT) fields are placed in environment variables at this time