m4 - GNU macro processor
GNU `m4' is an implementation of the traditional UNIX macro processor. It is mostly SVR4 compatible, although it has some extensions (for example, handling more than 9 positional parameters to macros). `m4' also has builtin functions for including files, running shell commands, doing arithmetic, etc. Autoconf needs GNU `m4' for generating `configure' scripts, but not for running them.
This manual page was written for the Debian distribution because the original program does not have a manual page. Instead, it has documentation in the GNU Info format. The manual is also available in HTML format in the m4-doc package.