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m4(1)

NAME

     m4 -- macro language processor

SYNOPSIS

     m4 [-d flags] [-t name] [-gs] [-D name[=value]] [-U name] [-I dirname]
	[file ...]

DESCRIPTION

     The m4 utility is a macro processor that can be used as a front end to
     any language (e.g., C, ratfor, fortran, lex, and yacc).  The m4 utility
     reads from the standard input and writes the processed text to the stan-
     dard output.

     Macro calls have the form name(argument1[, argument2, ..., argumentN]).

     There cannot be any space following the macro name and the open parenthe-
     sis (`(').  If the macro name is not followed by an open parenthesis it
     is processed with no arguments.

     Macro names consist of a leading alphabetic or underscore possibly fol-
     lowed by alphanumeric or underscore characters, e.g., valid macro names
     match the pattern ``[a-zA-Z_][a-zA-Z0-9_]*''.

     In arguments to macros, leading unquoted space, tab, and newline (`\n')
     characters are ignored.  To quote strings, use left and right single
     quotes (e.g., ` this is a string with a leading space').  You can change
     the quote characters with the changequote built-in macro.

     Most built-ins do not make any sense without arguments, and hence are not
     recognized as special when not followed by an open parenthesis.

     The options are as follows:

     -s      Emit #line directives for cpp(1).

     -D name[=value]
	     Define the symbol name to have some value (or NULL).

     -U name
	     Undefine the symbol name.

     -I dirname
	     Add directory dirname to the include path.

     -d flags
	     Set trace flags.  The flags argument may hold the following:

	     a	     print macro arguments
	     c	     print macro expansion over several lines
	     e	     print result of macro expansion
	     f	     print filename location
	     l	     print line number
	     q	     quote arguments and expansion with the current quotes
	     t	     start with all macros traced
	     x	     number macro expansions
	     V	     turn on all options

	     emacs(1) behavior, and the number of diversions is unlimited.

SYNTAX

     The m4 utility provides the following built-in macros.  They may be rede-
     fined, losing their original meaning.  Return values are null unless oth-
     erwise stated.

     builtin	  Calls a built-in by its name, overriding possible redefini-
		  tions.

     changecom	  Changes the start and end comment sequences.	The default is
		  the pound sign (`#') and the newline character.  With no
		  arguments, the comment sequence is reset to the default, in
		  GNU m4 mode, comments are turned off.  The maximum length
		  for a comment marker is five characters.

     changequote  Defines the quote symbols to be the first and second argu-
		  ments.  The symbols may be up to five characters long.  If
		  no arguments are given it restores the default open and
		  close single quotes.

     decr	  Decrements the argument by 1.  The argument must be a valid
		  numeric string.

     define	  Define a new macro named by the first argument to have the
		  value of the second argument.  Each occurrence of `$n'
		  (where n is 0 through 9) is replaced by the n'th argument.
		  `$0' is the name of the calling macro.  Undefined arguments
		  are replaced by a null string.  `$#' is replaced by the num-
		  ber of arguments; `$*' is replaced by all arguments comma
		  separated; `$@' is the same as `$*' but all arguments are
		  quoted against further expansion.

     defn	  Returns the quoted definition for each argument.  This can
		  be used to rename macro definitions (even for built-in
		  macros).

     divert	  There are 10 output queues (numbered 0-9).  At the end of
		  processing m4 concatenates all the queues in numerical order
		  to produce the final output.	Initially the output queue is
		  0.  The divert macro allows you to select a new output queue
		  (an invalid argument passed to divert causes output to be
		  discarded).

     divnum	  Returns the current output queue number.

     dnl	  Discards input characters up to and including the next new-
		  line.

     dumpdef	  Prints the names and definitions for the named items, or for
		  everything if no arguments are passed.

     errprint	  Prints the first argument on the standard error output
		  stream.

     esyscmd	  Passes its first argument to a shell and returns the shell's
		  standard output.  Note that the shell shares its standard
		  input and standard error with m4.
		  result.

     expr	  This is an alias for eval.

     ifdef	  If the macro named by the first argument is defined then
		  return the second argument, otherwise the third.  If there
		  is no third argument, the value is NULL.  The word unix is
		  predefined.

     ifelse	  If the first argument matches the second argument then
		  ifelse returns the third argument.  If the match fails, the
		  three arguments are discarded and the next three arguments
		  are used until there is zero or one arguments left, either
		  this last argument or NULL is returned if no other matches
		  were found.

     include	  Returns the contents of the file specified in the first
		  argument.  If the file is not found as is, look through the
		  include path: first the directories specified with -I on the
		  command line, then the environment variable M4PATH, as a
		  colon-separated list of directories.	Aborts with an error
		  message if the file cannot be included.

     incr	  Increments the argument by 1.  The argument must be a valid
		  numeric string.

     index	  Returns the index of the second argument in the first argu-
		  ment (e.g., index(the quick brown fox jumped, fox) returns
		  16).	If the second argument is not found, index returns -1.

     indir	  Indirectly calls the macro whose name is passed as the first
		  arguments, with the remaining arguments passed as first,
		  etc. arguments.

     len	  Returns the number of characters in the first argument.
		  Extra arguments are ignored.

     m4exit	  Immediately exits with the return value specified by the
		  first argument, 0 if none.

     m4wrap	  Allows you to define what happens at the final EOF, usually
		  for cleanup purposes (e.g., m4wrap(cleanup(tempfile)) causes
		  the macro cleanup to be invoked after all other processing
		  is done).

     maketemp	  Translates the string ``XXXXX'' in the first argument with
		  the current process ID leaving other characters alone.  This
		  can be used to create unique temporary file names.

     paste	  Includes the contents of the file specified by the first
		  argument without any macro processing.  Aborts with an error
		  message if the file cannot be included.

     patsubst	  Substitutes a regular expression in a string with a replace-
		  ment string.	Usual substitution patterns apply: an amper-
		  sand (`&') is replaced by the string matching the regular
		  expression.  The string `\#', where # is a digit, is
		  replaced by the corresponding back-reference.
		  if no match.	If a third argument is provided, it returns
		  the replacement string, with sub-patterns replaced.

     shift	  Returns all but the first argument, the remaining arguments
		  are quoted and pushed back with commas in between.  The
		  quoting nullifies the effect of the extra scan that will
		  subsequently be performed.

     sinclude	  Similar to include, except it ignores any errors.

     spaste	  Similar to paste, except it ignores any errors.

     substr	  Returns a substring of the first argument starting at the
		  offset specified by the second argument and the length spec-
		  ified by the third argument.	If no third argument is
		  present it returns the rest of the string.

     syscmd	  Passes the first argument to the shell.  Nothing is
		  returned.

     sysval	  Returns the return value from the last syscmd.

     traceon	  Enables tracing of macro expansions for the given arguments,
		  or for all macros if no argument is given.

     traceoff	  Disables tracing of macro expansions for the given argu-
		  ments, or for all macros if no argument is given.

     translit	  Transliterate the characters in the first argument from the
		  set given by the second argument to the set given by the
		  third.  You cannot use tr(1) style abbreviations.

     undefine	  Removes the definition for the macros specified by its argu-
		  ments.

     undivert	  Flushes the named output queues (or all queues if no argu-
		  ments).

     unix	  A pre-defined macro for testing the OS platform.

     __line__	  Returns the current file's line number.

     __file__	  Returns the current file's name.

DIAGNOSTICS

     The m4 utility exits 0 on success, and >0 if an error occurs.

     The m4exit macro may be used to change the exit status from the input
     file.

COMPATIBILITY

     The m4 utility follows the Version 2 of the Single UNIX Specification
     (``SUSv2''), along with a few extensions taken from GNU-m4.  Flags -I,
     -d, and -t are non-standard.

     The output format of tracing and of dumpdef are not specified in any
     standard, are likely to change and should not be relied upon.  The cur-
     rent format of tracing is closely modeled on GNU-m4, to allow autoconf to
     Many other m4 implementations have dire size limitations with respect to
     buffer sizes.

STANDARDS

     The m4 utility conforms to IEEE Std 1003.1-2001 (``POSIX.1'').

HISTORY

     An m4 command appeared in PWB UNIX.

AUTHORS

     Ozan Yigit <oz@sis.yorku.ca> and Richard A. O'Keefe
     <ok@goanna.cs.rmit.OZ.AU>.  GNU-m4 compatibility extensions by Marc Espie
     <espie@cvs.openbsd.org>.

BUGS

     The m4 utility does not recognize multibyte characters.

FreeBSD 5.4			 July 3, 2004			   FreeBSD 5.4

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