How to generate documentation from source code in Linux

If you are an open-source developer and want to release your project to the public, you may consider publishing source-code documentation for the project. In cases where you are trying to read source code written by others, it will also be helpful if you can get a "bird-eye" view of the otherwise cryptic source code.

In Linux, doxygen is the de facto standard tool for automatically generating cross-reference documentation from annotated source code. It supports major programming languages including C/C++, Objective-C, C#, PHP, Java and Python.

Using doxygen, you can auto-generate API reference documentation of source code, in HTML or Latex format. You can also visualize class dependency and the relationship between different source files.

In this tutorial, I will explain how to automatically generate documentation from source code in Linux by using doxygen.

To install doxygen on Ubuntu, Mint or Debian:

$ sudo apt-get install doxygen
$ sudo apt-get install graphviz

To install doxygen on CentOS, Fedora or RHEL:

$ sudo yum install doxygen
$ sudo yum install graphviz

To generate documentation of source code, proceed as follows.

First, generate a project-specific doxygen configuration file:

$ doxygen -g my_proj.conf

The above command will generate a template configuration file for a particular project.

Among others, you can edit the following options in the configuration file.

# document all entities in the project.
EXTRACT_ALL            = YES

# document all static members of a file.
EXTRACT_STATIC         = YES

# specify the root directory that contains the project's source files.
INPUT                  = /home/xmodulo/source

# search sub-directories for all source files.
RECURSIVE              = YES

# include the body of functions and classes in the documentation.
INLINE_SOURCES         = YES

# generate visualization graph by using dot program (part of graphviz package).
HAVE_DOT               = YES

Now go ahead and run doxygen with the configuration file.

$ doxygen my_proj.conf

Documentations are generated in both HTML and Latex formats, and stored in ./html and ./latex directories respectively.

To browse the HTML-formatted documentation, run the following.

$ cd html
$ firefox index.html

Doxygen Documentation Screenshots

Here are several screenshots for doxygen outputs.

This shows a list of header files that are automatically categorized by topics.

This shows a list of classes, structs, unions and interfaces with descriptions.

This shows a source code browser listing all source files recursively in sub-directories.

If you click on a particular source file, you will see a page which shows dependency graph for the file, as well as documentation for all defined functions.

This shows a detailed view of function/macro definitions. Below the figure is shown the actual source code snippet that corresponds to this documented portion.


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