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M4(1)			  BSD General Commands Manual			 M4(1)

     m4	-- macro language processor

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

     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

	     By	default, trace is set to eq.

     -t	macro
	     Turn tracing on for macro.

     -g	     Activate GNU-m4 compatibility mode.  In this mode,	changequote
	     with two empty parameters deactivates quotes, translit handles
	     simple character ranges (e.g., a-z), regular expressions mimic
	     emacs(1) behavior,	and the	number of diversions is	unlimited.

     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-

     changecom	  Changes the start and	end comment sequences.	The default is
		  the pound sign (`#') and the newline character.  With	no ar-
		  guments, 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

     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

     divnum	  Returns the current output queue number.

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

     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

     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.

     eval	  Computes the first argument as an arithmetic expression us-
		  ing 32-bit arithmetic.  Operators are	the standard C
		  ternary, arithmetic, logical,	shift, relational, bitwise,
		  and parentheses operators.  You can specify octal, decimal,
		  and hexadecimal numbers as in	C.  The	second argument	(if
		  any) specifies the radix for the result, and the third argu-
		  ment (if any)	specifies the minimum number of	digits in the

     expr	  This is an alias for eval.

     ifdef	  If the macro named by	the first argument is defined then re-
		  turn the second argument, otherwise the third.  If there is
		  no third argument, the value is NULL.	 The word unix is pre-

     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 ar-
		  gument.  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.  Ex-
		  tra 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 ar-
		  gument 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 re-
		  placed by the	corresponding back-reference.

     popdef	  Restores the pushdefed definition for	each argument.

     pushdef	  Takes	the same arguments as define, but it saves the defini-
		  tion on a stack for later retrieval by popdef.

     regexp	  Finds	a regular expression in	a string.  If no further argu-
		  ments	are given, it returns the first	match position or -1
		  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 re-

     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-

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

     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.

     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

     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

     For portability, one should not use the macros builtin, esyscmd, expr,
     indir, paste, patsubst, regexp, spaste, unix, __line__, and __file__.

     All built-ins do expand without arguments in many other m4	implementa-

     Many other	m4 implementations have	dire size limitations with respect to
     buffer sizes.

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

     An	m4 command appeared in PWB UNIX.

     Ozan Yigit	<> and Richard A. O'Keefe
     <>.	 GNU-m4	compatibility extensions by Marc Espie

     The m4 utility does not recognize multibyte characters.

BSD				 July 3, 2004				   BSD


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