Setting Up Doxygen External Search: A CGI Integration Guide for Apache and NGINX Environments

The Need for Doxygen External Search

Doxygen is a tool that automatically generates API documentation for various languages such as C++ and C#, but its default server-based search suffers from reduced accuracy due to whitespace handling issues. The EXTERNAL_SEARCH option, introduced after Doxygen 1.8.3, solves this problem by integrating with Xapian, an open-source search engine.

CGI Configuration Methods by Web Server

Since Doxygen's external search requires running a CGI binary file (doxysearch.cgi), web server configuration is essential.

• Apache HTTP Server: Configure ScriptAlias and Options +ExecCGI to allow CGI script execution. You need to modify the serve-cgi-bin.conf file to set the path to /var/www/cgi-bin/.
• NGINX: Since it does not support traditional CGI, install the FcgiWrap package to convert it to FastCGI. Configure the fastcgi_pass socket connection for .cgi files in fcgiwrap.conf.

Doxygen Configuration and Deployment Procedure

To enable external search, you need to set SEARCHENGINE=YES, EXTERNAL_SEARCH=YES, etc. in the Doxyfile and generate the documentation. The generated searchdata.xml is then processed with the doxyindexer command to create the doxysearch.db directory.

Finally, the root directory of the deployed documentation must contain both the doxysearch.cgi file and the doxysearch.db directory, and installation of the Xapian library (libxapian-dev) must be completed beforehand.