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m4(1)									 m4(1)

NAME    [Toc]    [Back]

     m4	- macro	processor

SYNOPSIS    [Toc]    [Back]

     m4	[options<b>] [files<b>]

DESCRIPTION    [Toc]    [Back]

     The m4 command is a macro processor intended as a front end for C,
     assembler,	and other languages.  Each of the argument files is processed
     in	order; if there	are no files, or if a file name	is -, the standard
     input is read.  The processed text	is written on the standard output.  m4
     processes supplementary code set characters in comments and literals
     according to the locale specified in the LC_CTYPE environment variable
     [see LANG on environ(5)].

     The options and their effects are as follows:

     -e	     Operate interactively.  Interrupts	are ignored and	the output is

     -s	     Enable line sync output for the C preprocessor (#line ...)

     -Bint   Change the	size of	the push-back and argument collection buffers
	     from the default of 4,096.

     -Hint   Change the	size of	the symbol table hash array from the default
	     of	199.  The size should be prime.

     -Sint   Change the	size of	the call stack from the	default	of 100 slots.
	     Macros take three slots, and non-macro arguments take one.

     -Tint   Change the	size of	the token buffer from the default of 512

     To	be effective, the above	flags must appear before any file names	and
     before any	-D or -U flags:

	       Defines name to val or to null in val's absence.

     -Uname    undefines name.

     Macro calls have the form:

	  name(arg1,arg2, ..., argn)

     The ( must	immediately follow the name of the macro.  If the name of a
     defined macro is not followed by a	(, it is deemed	to be a	call of	that
     macro with	no arguments.  Potential macro names consist of	alphanumeric
     characters	and underscore (_), where the first character is not a digit.

									Page 1

m4(1)									 m4(1)

     Leading unquoted blanks, tabs, and	new-lines are ignored while collecting
     arguments.	 Left and right	single quotes are used to quote	strings.  The
     value of a	quoted string is the string stripped of	the quotes.

     When a macro name is recognized, its arguments are	collected by searching
     for a matching right parenthesis.	If fewer arguments are supplied	than
     are in the	macro definition, the trailing arguments are taken to be null.
     Macro evaluation proceeds normally	during the collection of the
     arguments,	and any	commas or right	parentheses that happen	to turn	up
     within the	value of a nested call are as effective	as those in the
     original input text.  After argument collection, the value	of the macro
     is	pushed back onto the input stream and rescanned.

     m4	makes available	the following built-in macros.	These macros may be
     redefined,	but once this is done the original meaning is lost.  Their
     values are	null unless otherwise stated.

     define	  the second argument is installed as the value	of the macro
		  whose	name is	the first argument.  Each occurrence of	$n in
		  the replacement text,	where n	is a digit, is replaced	by the
		  n-th argument.  Argument 0 is	the name of the	macro; missing
		  arguments are	replaced by the	null string; $#	is replaced by
		  the number of	arguments; $* is replaced by a list of all the
		  arguments separated by commas; $@ is like $*,	but each
		  argument is quoted (with the current quotes).

     undefine	  removes the definition of the	macro named in its argument.

     defn	  returns the quoted definition	of its argument(s).  It	is
		  useful for renaming macros, especially built-ins.

     pushdef	  like define, but saves any previous definition.

     popdef	  removes current definition of	its argument(s), exposing the
		  previous one,	if any.

     ifdef	  If the first argument	to the ifdef macro is defined and it
		  is not defined to be zero, the defining text is the second
		  argument. Otherwise, the defining text is the	third
		  argument, if specified, or the null string, if not.  The
		  word unix is predefined.

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

     changequote  change quote symbols to the first and	second arguments.  The
		  symbols may be up to five characters long.  changequote
		  without arguments restores the original values (that is,

									Page 2

m4(1)									 m4(1)

     changecom	  change left and right	comment	markers	from the default # and
		  new-line.  With no arguments,	the comment mechanism is
		  effectively disabled.	 With one argument, the	left marker
		  becomes the argument and the right marker becomes new-line.
		  With two arguments, both markers are affected.  Comment
		  markers may be up to five characters long.

     divert	  m4 maintains 10 output streams, numbered 0-9.	 The final
		  output is the	concatenation of the streams in	numerical
		  order; initially stream 0 is the current stream.  The	divert
		  macro	changes	the current output stream to its (digitstring)
 argument.  Output diverted to	a stream other than 0
		  through 9 is discarded.

     undivert	  causes immediate output of text from diversions named	as
		  arguments, or	all diversions if no argument.	Text may be
		  undiverted into another diversion.  Undiverting discards the
		  diverted text.

     divnum	  returns the value of the current output stream.

     dnl	  reads	and discards characters	up to and including the	next

     ifelse	  has three or more arguments.	If the first argument is the
		  same string as the second, then the value is the third
		  argument.  If	not, and if there are more than	four
		  arguments, the process is repeated with arguments 4, 5, 6
		  and 7.  Otherwise, the value is either the fourth string,
		  or, if it is not present, null.

     incr	  returns the value of its argument incremented	by 1.  The
		  value	of the argument	is calculated by interpreting an
		  initial digit-string as a decimal number.

     decr	  returns the value of its argument decremented	by 1.

     eval	  evaluates its	argument as an arithmetic expression, using
		  32-bit arithmetic.  Operators	include	+, -, *, /, %, **
		  (exponentiation), bitwise &, |, ^, and ~; relationals;
		  parentheses.	Octal and hex numbers may be specified as in
		  C.  The second argument specifies the	radix for the result;
		  the default is 10.  The third	argument may be	used to
		  specify the minimum number of	digits in the result.

     len	  returns the number of	characters in its argument.

     index	  returns the position in its first argument where the second
		  argument begins (zero	origin), or -1 if the second argument
		  does not occur.

									Page 3

m4(1)									 m4(1)

     substr	  returns a substring of its first argument.  The second
		  argument is a	zero origin number selecting the first
		  character; the third argument	indicates the length of	the
		  substring.  A	missing	third argument is taken	to be large
		  enough to extend to the end of the first string.

     translit	  transliterates the characters	in its first argument from the
		  set given by the second argument to the set given by the
		  third.  No abbreviations are permitted.

     include	  returns the contents of the file named in the	argument.

     sinclude	  is identical to include, except that it says nothing if the
		  file is inaccessible.

     syscmd	  executes the UNIX System command given in the	first
		  argument.  No	value is returned.

     sysval	  is the return	code from the last call	to syscmd.

     maketemp	  fills	in a string of XXXXX in	its argument with the current
		  process ID.

     m4exit	  causes immediate exit	from m4.  Argument 1, if given,	is the
		  exit code; the default is 0.

     m4wrap	  The first argument will be processed when EOF	is reached. If
		  the m4wrap macro is used multiple times, the arguments
		  specified will be processed in the order in which the	m4wrap
		  macros were processed.

     errprint	  prints its argument on the diagnostic	output file.

     dumpdef	  prints current names and definitions,	for the	named items,
		  or for all if	no arguments are given.

     traceon	  with no arguments, turns on tracing for all macros
		  (including built-ins).  Otherwise, turns on tracing for
		  named	macros.

     traceoff	  turns	off trace globally and for any macros specified.
		  Macros specifically traced by	traceon	can be untraced	only
		  by specific calls to traceoff.

SEE ALSO    [Toc]    [Back]

     as(1), cc(1)

									PPPPaaaaggggeeee 4444
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