Writing Apache Modules with Perl and C

F.5. Debugging

Debugging of CGI scripts is always a difficult task because the execution is controlled by the web server and, for the most part, you can't use a debugger. Embperl helps you debug your Embperl pages by creating a detailed log file. The log file shows you what Embperl does as it processes your page. Depending on the debug flag settings, Embperl logs the following:

• Source

• Environment

• Form data

• Evals (source and result)

• Table processing

• Input tag processing

• HTTP headers

To make debugging even easier, you can tell Embperl to display a link at the top of each page to your log file while you are debugging a page. If you follow the link, Embperl will show the portion of the log file that corresponds to that request. The log file lines are displayed in different colors to give you a better overview. With these links to the log file enabled, every error displayed in an error page is also a link to the corresponding position in the log file, so you can easily locate where things are going wrong.