mod_cgi
mod_cgi is a module for the Apache HTTP Server, which allows the server to handle Common Gateway Interface (CGI) scripts. CGI is a standard for interfacing external applications with web servers, enabling the creation of dynamic web content.
History and Development
The concept of CGI was developed in the early 1990s as a way to generate dynamic content on the web. Here's a brief timeline:
- 1993: NCSA HTTPd, the predecessor to Apache HTTP Server, introduced CGI support.
- 1995: The Apache HTTP Server project was started, with CGI support being one of its initial features.
- 1999: Apache 1.3.x series stabilized, with mod_cgi as a core module.
- 2002: With the release of Apache 2.0, mod_cgi continued to be included, but alternatives like mod_php began to gain popularity due to performance advantages.
Functionality
mod_cgi works by:
- Recognizing files with specific extensions (like .cgi, .pl, .py) as CGI scripts.
- Executing these scripts in a separate process or thread, depending on the server's configuration.
- Passing environment variables and input from the HTTP request to the script.
- Collecting the output from the script and sending it back to the client as the HTTP response.
Usage and Configuration
To enable CGI with mod_cgi, you would typically:
- Ensure mod_cgi is enabled in Apache's configuration file (httpd.conf or apache2.conf).
- Set up a directory or directories where CGI scripts are allowed to execute, often using the
ScriptAlias directive to map a URL to a filesystem location.
- Configure the server to recognize CGI files by file extension or script alias.
ScriptAlias /cgi-bin/ "/usr/local/apache2/cgi-bin/"
<Directory "/usr/local/apache2/cgi-bin">
AllowOverride None
Options +ExecCGI
AddHandler cgi-script .cgi .pl
Require all granted
</Directory>
Advantages and Limitations
- Advantages:
- Easy to implement and understand.
- Language agnostic; supports scripts written in any language that can output to stdout.
- Isolates scripts from the web server process, potentially enhancing security.
- Limitations:
- Performance overhead due to process creation for each script invocation.
- Not as efficient as embedded scripting modules like mod_php or mod_perl.
- Requires careful configuration to prevent security vulnerabilities.
External Links
Related Topics