Doxygen manual: Getting started

# Getting started

The executable `doxygen` is the main program that parses the sources and generates the documentation. See section Doxygen usage for more detailed usage information.

The executable `doxytag` is only needed if you want to generate references to external documentation (i.e. documentation that was generated by doxygen) for which you do not have the sources. See section Doxytag usage for more detailed usage information.

Optionally, the executable `doxywizard` can be used, which is a graphical front-end for editing the configuration file that is used by doxygen.

The following figure shows the relation between the tools and the flow of information between them:

Doxygen information flow

## Step 1: Creating a configuration file

Doxygen uses a configuration file to determine all of its settings. Each project should get its own configuration file. A project can consist of a single source file, but can also be an entire source tree that is recursively scanned.

To simplify the creation of a configuration file, doxygen can create a template configuration file for you. To do this call `doxygen` from the command line with the `-g` option:

    doxygen -g <config-file>

where <config-file> is the name of the configuration file. If you omit the file name, a file named `Doxyfile` will be created. If a file with the name <config-file> already exists, doxygen will rename it to <config-file>.bak before generating the configuration template. If you use `-` (i.e. the minus sign) as the file name then doxygen will try to read the configuration file from standard input (`stdin`).

The configuration file has a format that is similar to that of a (simple) Makefile. It contains of a number of assignments (tags) of the form:

`TAGNAME = VALUE` or
`TAGNAME = VALUE1 VALUE2 ...`

You can probably leave the values of most tags in a generated template configuration file to their default value. See section Configuration for more details about the configuration file.

If you do not wish to edit the config file with a text editor, you should have a look at doxywizard, which is a GUI front-end that can create, read and write doxygen configuration files, and allows setting configuration options by entering them via dialogs.

For a small project consisting of a few C and/or C++ source and header files, you can leave INPUT tag empty and doxygen will search for sources in the current directory.

If you have a larger project consisting of a source directory or tree you should put the root directory or directories after the INPUT tag, and add one or more file patterns to the FILE_PATTERNS tag (for instance `*.cpp *.h`). Only files that match one of the patterns will be parsed (if the patterns are omitted a list of source extensions is used). For recursive parsing of a source tree you must set the RECURSIVE tag to `YES`. To further fine-tune the list of files that is parsed the EXCLUDE and EXCLUDE_PATTERNS tags can be used. To omit all `test` directories from a source tree for instance, one could use:

     EXCLUDE_PATTERNS = */test/*

Doxygen normally parses files if they are C or C++ sources. If a file has a `.idl` or `.odl` extension it is treated as an IDL file. If it has a `.java` extension it is treated as a file written in Java. Files ending with `.cs` are treated as C# files. Finally, files with the extensions `.php`, `.php4`, `.inc` or `.phtml` are treated as PHP sources.

If you start using doxygen for an existing project (thus without any documentation that doxygen is aware of), you can still get an idea of what the documented result would be. To do so, you must set the EXTRACT_ALL tag in the configuration file to `YES`. Then, doxygen will pretend everything in your sources is documented. Please note that as a consequence warnings about undocumented members will not be generated as long as EXTRACT_ALL is set to `YES`.

To analyse an existing piece of software it is useful to cross-reference a (documented) entity with its definition in the source files. Doxygen will generate such cross-references if you set the SOURCE_BROWSER tag to `YES`. It can also include the sources directly into the documentation by setting INLINE_SOURCES to `YES` (this can be handy for code reviews for instance).

## Step 2: Running doxygen

To generate the documentation you can now enter:

    doxygen <config-file>

Doxygen will create a `html`, `rtf`, `latex` and/or `man` directory inside the output directory. As the names suggest these directories contain the generated documentation in HTML, RTF, and Unix-Man page format.

The default output directory is the directory in which `doxygen` is started. The directory to which the output is written can be changed using the OUTPUT_DIRECTORY, HTML_OUTPUT, RTF_OUTPUT, LATEX_OUTPUT, and MAN_OUTPUT tags of the configuration file. If the output directory does not exist, `doxygen` will try to create it for you.

The generated HTML documentation can be viewed by pointing a HTML browser to the `index.html` file in the `html` directory. For the best results a browser that supports cascading style sheets (CSS) should be used (I'm currently using Netscape 4.61 to test the generated output).

The generated documentation must first be compiled by a compiler (I use teTeX distribution version 0.9 that contains version 3.14159). To simplify the process of compiling the generated documentation, `doxygen` writes a `Makefile` into the `latex` directory. By typing `make` in the `latex` directory the dvi file `refman.dvi` will be generated (provided that you have a make tool called `make` of course). This file can then be viewed using `xdvi` or converted into a PostScript file `refman.ps` by typing `make ps` (this requires `dvips`). To put 2 pages on one physical page use `make ps_2on1` instead. The resulting PostScript file can be send to a PostScript printer. If you do not have a PostScript printer, you can try to use ghostscript to convert PostScript into something your printer understands. Conversion to PDF is also possible if you have installed the ghostscript interpreter; just type `make pdf` (or `make pdf_2on1`). To get the best results for PDF output you should set the PDF_HYPERLINKS tag to `YES`.

The generated man pages can be viewed using the `man` program. You do need to make sure the man directory is in the man path (see the `MANPATH` environment variable). Note that there are some limitations to the capabilities of the man page format, so some information (like class diagrams, cross references and formulas) will be lost.

## Step 3: Documenting the sources

Although documenting the source is presented as step 3, in a new project this should of course be step 1. Here I assume you already have some code and you want doxygen to generate a nice document describing the API and maybe the internals as well.

If the EXTRACT_ALL option is set to `NO` in the configuration file (the default), then doxygen will only generate documentation for documented members, files, classes and namespaces. So how do you document these? For members, classes and namespaces there are basically two options:

1. Place a special documentation block in front of the declaration or definition of the member, class or namespace. For file, class and namespace members it is also allowed to place the documention directly after the member. See section Special documentation blocks to learn more about special documentation blocks.
2. Place a special documentation block somewhere else (another file or another location) and put a structural command in the documentation block. A structural command links a documentation block to a certain entity that can be documented (e.g. a member, class, namespace or file). See section Documentation at other places to learn more about structural commands.

Files can only be documented using the second option, since there is no way to put a documentation block before a file. Of course, file members (functions, variable, typedefs, defines) do not need an explicit structural command; just putting a special documentation block in front or behind them will do.

The text inside a special documentation block is parsed before it is written to the HTML and/or output files.

During parsing the following steps take place:

- The special commands inside the documentation are executed. See section Special Commands for an overview of all commands.
- If a line starts with some whitespace followed by one or more asterisks (`*`) and then optionally more whitespace, then all whitespace and asterisks are removed.
- All resulting blank lines are treated as a paragraph separators. This saves you from placing new-paragraph commands yourself in order to make the generated documentation readable.
- Links are created for words corresponding to documented classes.
- Links to members are created when certain patterns are found in the text. See section Automatic link generation for more information on how the automatic link generation works.
- HTML tags that are in the documentation are interpreted and converted to equivalents for the output. See section HTML Commands for an overview of all supported HTML tags.

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