Recipe 8.3 Using Windows File Extensionsto Launch CGI Programs

Problem

You want to have CGI programs on Windows executed by the program associated with the file extension. For example, you want .pl files to be executed by perl.exe without having to change the #! line to point at the right location.

Solution

Add the following line to your httpd.conf file:

ScriptInterpreterSource registry

Discussion

Since Apache has its roots in the Unixish world, there are a number of things that are done the Unixish way, even on Microsoft Windows. CGI execution is one of these things, but the ScriptInterpreterSource directive allows you to have Apache behave more in the way that Windows users are accustomed to.

Usually, on Windows, a file type is indicated by the file extension. For example, a file named example.pl is associated with the Perl executable; when a user clicks on this file in the file explorer, Perl is invoked to execute this script. This association is created when you install a particular program, such as Perl or MS Word, and the association is stored in the Windows registry.

On Unixish systems, on the other hand, most scripts contain the location of their interpreter in the first line of the file, which starts with the characters #!. This line is often called the shebang line (short for sharp bang, which are the shorthand names for the two characters).

For example, a Perl program might start with the line:

#!/usr/bin/perl

The shell running the script looks in this first line and uses the program at the indicated path to interpret and execute the script. In this way, files with arbitrary file extensions (or no extension at all) may be invoked with any interpreter desired. In the case of Perl, for example, one might have several versions of Perl installed, and the particular version desired may be invoked by using the appropriate #! line.

However, you may be accustomed to the operating system's innate way of executing a program, and this can be somewhat nonintuitive. Thus, in the early days of Apache on Windows, the ScriptInterpreterSource directive was added to make Apache behave the way that Windows users expected.

ScriptInterpreterSource may have one of two values. When set to the default value, script, Apache will look in the script itself for the location of the interpreter that it is to use. When it is set to registry, it will look in the Windows registry for the mapping that is associated with the file's extension and use this to execute the script.

This feature can be very useful for users who are running multiple servers, some on Unixish operating systems and others on Windows, but who want the same CGI programs to run both places. Because Perl is unlikely to be located at /usr/bin/perl on your Windows machine, using the ScriptInterpreterSource directive allows you to run the script unedited on Windows, simply by virtue of it having a .pl file extension.

See Also

• Recipe 8.2

• Recipe 8.4