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GNU M4
******

This manual (31 December 2016) is for GNU M4 (version 1.4.18), a package
containing an implementation of the m4 macro language.

   Copyright (C) 1989-1994, 2004-2014, 2016 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 'm4-1.4.18/AUTHORS'
and 'm4-1.4.18/THANKS' from the GNU M4 distribution.

   This is release 1.4.18.  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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