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22.9.4 Languages for CGI

Theoretically, CGI programs can be written in any programming language.

Usually, scripting languages (interpreted languages), such as Perl or PHP,

are used for this purpose. If speed is critical, C or C++ may be more suit-

able.

In the simplest case, Apache looks for these programs in a speciﬁc di-

rectory (cgi-bin). This directory can be set in the conﬁguration ﬁle, de-

scribed in Section 22.7 on page 536).

If necessary, additional directories can be speciﬁed. In this case, Apache

searches these directories for executable programs. However, this repre-

sents a security risk, as any user will be able to let Apache execute pro-

grams (some of which may be malicious). If executable programs are re-

stricted to cgi-bin, the administrator can easily see who places which

scripts and programs in this directory and check them for any malicious

intent.

22.9.5 Generating Active Contents with Modules

A variety of modules is available for use with Apache. The term “mod-

ule” is used in two different senses. First, there are modules that can be

integrated in Apache to handle speciﬁc functions, such as modules for

embedding programming languages. These modules are introduced below.

Second, in connection with programming languages, modules refer to an

independent group of functions, classes, and variables. These modules are

integrated in a program to provide a certain functionality, such as the CGI

modules available for all scripting languages. These modules facilitate the

programming of CGI applications by providing various functions, such as

methods for reading the request parameters and for the HTML output.

22.9.6 mod_perl

Perl is a popular, proven scripting language. There are numerous modules

and libraries for Perl, including a library for expanding the Apache con-

ﬁguration ﬁle. The home page for Perl is http://www.perl.com/. A

range of libraries for Perl is available in the Comprehensive Perl Archive

Network (CPAN) at http://www.cpan.org/.

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22.9. Active Contents