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1.1 Introduction to `m4'

`m4' is a macro processor, in the sense that it copies its input to the
output, expanding macros as it goes.  Macros are either builtin or
user-defined, and can take any number of arguments.  Besides just doing
macro expansion, `m4' has builtin functions for including named files,
running shell commands, doing integer arithmetic, manipulating text in
various ways, performing recursion, etc....  `m4' can be used either as
a front-end to a compiler, or as a macro processor in its own right.

   The `m4' macro processor is widely available on all UNIXes, and has
been standardized by POSIX.  Usually, only a small percentage of users
are aware of its existence.  However, those who find it often become
committed users.  The popularity of GNU Autoconf, which requires GNU
`m4' for _generating_ `configure' scripts, is an incentive for many to
install it, while these people will not themselves program in `m4'.
GNU `m4' is mostly compatible with the System V, Release 3 version,
except for some minor differences.  Note: Compatibility, for more

   Some people find `m4' to be fairly addictive.  They first use `m4'
for simple problems, then take bigger and bigger challenges, learning
how to write complex sets of `m4' macros along the way.  Once really
addicted, users pursue writing of sophisticated `m4' applications even
to solve simple problems, devoting more time debugging their `m4'
scripts than doing real work.  Beware that `m4' may be dangerous for
the health of compulsive programmers.

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