lfs-book-zh_CN/appendixa/m4-desc.xml

<sect2>
<title>Contents</title>

<para>
The M4 package contains the M4 processor
</para>

</sect2>

<sect2>
<title>Description</title>

<para>
M4 is a macro processor. It copies input to output expanding macros as it 
goes. Macros are either built-in or user-defined and can take any number
of arguments. Besides just doing macro expansion m4 has built-in functions 
for including named files, running UNIX commands, doing integer arithmetic, 
manipulating text in various ways, recursion, etc. M4 can be used either 
as a front-end to a compiler or as a macro processor in its own right.
</para>

</sect2>