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<modulesynopsis metafile="mod_cgi.xml.meta">

<name>mod_cgi</name>

<description>Execution of CGI scripts</description>

<status>Base</status>

<sourcefile>mod_cgi.c</sourcefile>

<identifier>cgi_module</identifier>

<summary>

<!-- XXX: Should mention Options ExecCGI

<p>Any file that has the mime type

<code>application/x-httpd-cgi</code> or handler

<code>cgi-script</code> (Apache 1.1 or later) will be treated

as a CGI script, and run by the server, with its output being

returned to the client. Files acquire this type either by

having a name containing an extension defined by the

<directive module="mod_mime">AddType</directive> directive, or by being

in a <directive module="mod_alias">ScriptAlias</directive>

directory.</p>

<p>When the server invokes a CGI script, it will add a variable

called <code>DOCUMENT_ROOT</code> to the environment. This

variable will contain the value of the

<directive module="core">DocumentRoot</directive> configuration

variable.</p>

<p>For an introduction to using CGI scripts with Apache, see

our tutorial on <a href="/howto/cgi.html">Dynamic Content

With CGI</a>.</p>

<p>When using a multi-threaded MPM under unix, the module

<module>mod_cgid</module> should be used in place of

this module. At the user level, the two modules are essentially

identical.</p>

</summary>

<seealso><directive module="core">AcceptPathInfo</directive></seealso>

<seealso><directive module="core">Options</directive></seealso>

<seealso><directive module="mod_alias">ScriptAlias</directive></seealso>

<seealso><directive module="mod_mime">AddHandler</directive></seealso>

<seealso><a href="/suexec.html">Running CGI programs under different

user IDs</a></seealso>

<seealso><a href="http://hoohoo.ncsa.uiuc.edu/cgi/">CGI Specification</a></seealso>

<section id="env"><title>CGI Environment variables</title>

<p>The server will set the CGI environment variables as described

in the <a href="http://hoohoo.ncsa.uiuc.edu/cgi/">CGI

specification</a>, with the following provisions:</p>

<dl>

<dt>PATH_INFO</dt>

<dd>This will not be available if the <directive module="core"

>AcceptPathInfo</directive> directive is explicitly set to

<code>off</code>. The default behavior, if <directive

>AcceptPathInfo</directive> is not given, is that <module

>mod_cgi</module> will accept path info (trailing <code>

/more/path/info</code> following the script filename in the URI),

while the core server will return a 404 NOT FOUND error for requests

with additional path info. Omitting the <directive

>AcceptPathInfo</directive> directive has the same effect as setting

it <code>On</code> for <module>mod_cgi</module> requests.</dd>

<dt>REMOTE_HOST</dt>

<dd>This will only be set if <directive module="core"

>HostnameLookups</directive> is set to <code>on</code> (it

is off by default), and if a reverse DNS lookup of the accessing

host's address indeed finds a host name.</dd>

<dt>REMOTE_IDENT</dt>

<dd>This will only be set if <directive module="core"

>IdentityCheck</directive> is set to

<code>on</code> and the accessing host supports the ident

protocol. Note that the contents of this variable cannot be

relied upon because it can easily be faked, and if there is a

proxy between the client and the server, it is usually

totally useless.</dd>

<dt>REMOTE_USER</dt>

<dd>This will only be set if the CGI script is subject to

authentication.</dd>

</dl>

</section>

<section id="cgi-debug"><title>CGI Debugging</title>

<p>Debugging CGI scripts has traditionally been difficult, mainly

because it has not been possible to study the output (standard

output and error) for scripts which are failing to run

properly. These directives, included in Apache 1.2 and later,

provide more detailed logging of errors when they occur.</p>

<section><title>CGI Logfile Format</title>

<p>When configured, the CGI error log logs any CGI which does not

execute properly. Each CGI script which fails to operate causes

several lines of information to be logged. The first two lines

are always of the format:</p>

<example>

%% [<var>time</var>] <var>request-line</var><br />

%% <var>HTTP-status</var> <var>CGI-script-filename</var>

</example>

<p>If the error is that CGI script cannot be run, the log file

will contain an extra two lines:</p>

<example>

%%error<br />

<var>error-message</var>

</example>

<p>Alternatively, if the error is the result of the script

returning incorrect header information (often due to a bug in

the script), the following information is logged:</p>

<example>

%request<br />

<var>All HTTP request headers received</var><br />

<var>POST or PUT entity (if any)</var><br />

%response<br />

<var>All headers output by the CGI script</var><br />

%stdout<br />

<var>CGI standard output</var><br />

%stderr<br />

<var>CGI standard error</var><br />

</example>

<p>(The %stdout and %stderr parts may be missing if the script did

not output anything on standard output or standard error).</p>

</section>

</section>

<directivesynopsis>

<name>ScriptLog</name>

<description>Location of the CGI script error logfile</description>

<syntax>ScriptLog <var>file-path</var></syntax>

<contextlist><context>server config</context>

<context>virtual host</context></contextlist>

<modulelist><module>mod_cgi</module><module>mod_cgid</module>

</modulelist>

<usage>

<p>The <directive>ScriptLog</directive> directive sets the CGI

script error logfile. If no <directive>ScriptLog</directive> is given,

no error log is created. If given, any CGI errors are logged into the

filename given as argument. If this is a relative file or path it is

taken relative to the <directive module="core">ServerRoot</directive>.

</p>

<example><title>Example</title>

ScriptLog logs/cgi_log

</example>

<p>This log will be opened as the user the child processes run

as, <em>i.e.</em> the user specified in the main <directive

module="mpm_common">User</directive> directive. This means that

either the directory the script log is in needs to be writable

by that user or the file needs to be manually created and set

to be writable by that user. If you place the script log in

your main logs directory, do <strong>NOT</strong> change the

directory permissions to make it writable by the user the child

processes run as.</p>

<p>Note that script logging is meant to be a debugging feature

when writing CGI scripts, and is not meant to be activated

continuously on running servers. It is not optimized for speed

or efficiency, and may have security problems if used in a

manner other than that for which it was designed.</p>

</usage>

</directivesynopsis>

<directivesynopsis>

<name>ScriptLogLength</name>

<description>Size limit of the CGI script logfile</description>

<syntax>ScriptLogLength <var>bytes</var></syntax>

<default>ScriptLogLength 10385760</default>

<contextlist><context>server config</context>

<context>virtual host</context></contextlist>

<modulelist><module>mod_cgi</module><module>mod_cgid</module>

</modulelist>

<usage>

<p><directive>ScriptLogLength</directive> can be used to limit the

size of the CGI script logfile. Since the logfile logs a lot of

information per CGI error (all request headers, all script output)

it can grow to be a big file. To prevent problems due to unbounded

growth, this directive can be used to set an maximum file-size for

the CGI logfile. If the file exceeds this size, no more

information will be written to it.</p>

</usage>

</directivesynopsis>

<directivesynopsis>

<name>ScriptLogBuffer</name>

<description>Maximum amount of PUT or POST requests that will be recorded

in the scriptlog</description>

<syntax>ScriptLogBuffer <var>bytes</var></syntax>

<default>ScriptLogBuffer 1024</default>

<contextlist><context>server config</context>

<context>virtual host</context></contextlist>

<modulelist><module>mod_cgi</module><module>mod_cgid</module>

</modulelist>

<usage>

<p>The size of any PUT or POST entity body that is logged to

the file is limited, to prevent the log file growing too big

too quickly if large bodies are being received. By default, up

to 1024 bytes are logged, but this can be changed with this

directive.</p>

</usage>

</directivesynopsis>

</modulesynopsis>