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GNU M4
******

This manual (28 February 2011) is for GNU M4 (version 1.4.16), a
package containing an implementation of the m4 macro language.

   Copyright (C) 1989-1994, 2004-2011 Free Software Foundation, Inc.

     Permission is granted to copy, distribute and/or modify this
     document under the terms of the GNU Free Documentation License,
     Version 1.3 or any later version published by the Free Software
     Foundation; with no Invariant Sections, no Front-Cover Texts, and
     no Back-Cover Texts.  A copy of the license is included in the
     section entitled "GNU Free Documentation License."

   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.

   GNU `m4' was originally written by Rene' Seindal, with subsequent
changes by Franc,ois Pinard and other volunteers on the Internet.  All
names and email addresses can be found in the files `m4-1.4.16/AUTHORS'
and `m4-1.4.16/THANKS' from the GNU M4 distribution.

   This is release 1.4.16.  It is now considered stable:  future
releases in the 1.4.x series are only meant to fix bugs, increase speed,
or improve documentation.  However...

   An experimental feature, which would improve `m4' usefulness, allows
for changing the syntax for what is a "word" in `m4'.  You should use:
     ./configure --enable-changeword
   if you want this feature compiled in.  The current implementation
slows down `m4' considerably and is hardly acceptable.  In the future,
`m4' 2.0 will come with a different set of new features that provide
similar capabilities, but without the inefficiencies, so changeword
will go away and _you should not count on it_.

Preliminaries: Introduction and preliminaries
Invoking m4: Invoking `m4'
Syntax: Lexical and syntactic conventions
Macros: How to invoke macros
Definitions: How to define new macros
Conditionals: Conditionals, loops, and recursion
Debugging: How to debug macros and input
Input Control: Input control
File Inclusion: File inclusion
Diversions: Diverting and undiverting output
Text handling: Macros for text handling
Arithmetic: Macros for doing arithmetic
Shell commands: Macros for running shell commands
Miscellaneous: Miscellaneous builtin macros
Frozen files: Fast loading of frozen state
Compatibility: Compatibility with other versions of `m4'
Answers: Correct version of some examples
Copying This Package: How to make copies of the overall M4 package
Copying This Manual: How to make copies of this manual
Indices: Indices of concepts and macros

 --- The Detailed Node Listing ---

Introduction and preliminaries

Intro: Introduction to `m4'
History: Historical references
Bugs: Problems and bugs
Manual: Using this manual

Invoking `m4'

Operation modes: Command line options for operation modes
Preprocessor features: Command line options for preprocessor features
Limits control: Command line options for limits control
Frozen state: Command line options for frozen state
Debugging options: Command line options for debugging
Command line files: Specifying input files on the command line

Lexical and syntactic conventions

Names: Macro names
Quoted strings: Quoting input to `m4'
Comments: Comments in `m4' input
Other tokens: Other kinds of input tokens
Input processing: How `m4' copies input to output

How to invoke macros

Invocation: Macro invocation
Inhibiting Invocation: Preventing macro invocation
Macro Arguments: Macro arguments
Quoting Arguments: On Quoting Arguments to macros
Macro expansion: Expanding macros

How to define new macros

Define: Defining a new macro
Arguments: Arguments to macros
Pseudo Arguments: Special arguments to macros
Undefine: Deleting a macro
Defn: Renaming macros
Pushdef: Temporarily redefining macros
Indir: Indirect call of macros
Builtin: Indirect call of builtins

Conditionals, loops, and recursion

Ifdef: Testing if a macro is defined
Ifelse: If-else construct, or multibranch
Shift: Recursion in `m4'
Forloop: Iteration by counting
Foreach: Iteration by list contents
Stacks: Working with definition stacks
Composition: Building macros with macros

How to debug macros and input

Dumpdef: Displaying macro definitions
Trace: Tracing macro calls
Debug Levels: Controlling debugging output
Debug Output: Saving debugging output

Input control

Dnl: Deleting whitespace in input
Changequote: Changing the quote characters
Changecom: Changing the comment delimiters
Changeword: Changing the lexical structure of words
M4wrap: Saving text until end of input

File inclusion

Include: Including named files
Search Path: Searching for include files

Diverting and undiverting output

Divert: Diverting output
Undivert: Undiverting output
Divnum: Diversion numbers
Cleardivert: Discarding diverted text

Macros for text handling

Len: Calculating length of strings
Index macro: Searching for substrings
Regexp: Searching for regular expressions
Substr: Extracting substrings
Translit: Translating characters
Patsubst: Substituting text by regular expression
Format: Formatting strings (printf-like)

Macros for doing arithmetic

Incr: Decrement and increment operators
Eval: Evaluating integer expressions

Macros for running shell commands

Platform macros: Determining the platform
Syscmd: Executing simple commands
Esyscmd: Reading the output of commands
Sysval: Exit status
Mkstemp: Making temporary files

Miscellaneous builtin macros

Errprint: Printing error messages
Location: Printing current location
M4exit: Exiting from `m4'

Fast loading of frozen state

Using frozen files: Using frozen files
Frozen file format: Frozen file format

Compatibility with other versions of `m4'

Extensions: Extensions in GNU M4
Incompatibilities: Facilities in System V m4 not in GNU M4
Other Incompatibilities: Other incompatibilities

Correct version of some examples

Improved exch: Solution for `exch'
Improved forloop: Solution for `forloop'
Improved foreach: Solution for `foreach'
Improved copy: Solution for `copy'
Improved m4wrap: Solution for `m4wrap'
Improved cleardivert: Solution for `cleardivert'
Improved capitalize: Solution for `capitalize'
Improved fatal_error: Solution for `fatal_error'

How to make copies of the overall M4 package

GNU General Public License: License for copying the M4 package

How to make copies of this manual

GNU Free Documentation License: License for copying this manual

Indices of concepts and macros

Macro index: Index for all `m4' macros
Concept index: Index for many concepts

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