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m4(1)											    m4(1)

       m4 - macro processor

       m4 [ -Dname[=value]] [-Uname] [files ...]

       m4  is  a  macro processor intended as a front end for any language (e.g., C, ratfor, for-
       tran, lex, and yacc).  m4 reads from the standard input and writes the processed  text  to
       the standard output.  Each of the optional argument files is processed in order.

       Macro calls have the form

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

       The  `('  must  immediately  follow the name of the macro.  If a defined macro name is not
       followed by a `(', it is deemed to have no arguments.  Leading unquoted blanks, tabs,  and
       newlines  are ignored while collecting arguments.  Potential macro names consist of alpha-
       betic letters, digits, and underscore `_', where the first character is not a digit.

       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.  Macro evaluation proceeds normally during the collection of the  argu-
       ments,  and  any commas or right parentheses which happen to turn up within the value of a
       nested call are as effective as those in the original input text.  After argument  collec-
       tion, the value of the macro is pushed back onto the input stream and rescanned.

		 Define the symbol name to have some value (or NULL).

       -Uname	 Undefine the symbol name.

       m4 makes available the following built-in macros.  They 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.

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

       ifdef	 If  the  first  argument is defined, the value is the second argument, otherwise
		 the third.  If there is no third argument, the value is null.

       changecom Change the start and end comment sequences.  The default is the pound	sign  '#'
		 and the newline character.  With no arguments comments are turned off.  The max-
		 imum legnth for a comment marker is five characters.

		 Change quote characters to the first and second arguments.  Changequote  without
		 arguments restores the original values (i.e., `').

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

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

       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.

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

       divnum	 returns the value of the current output stream.

       dnl	 reads and discards characters up to and including the next newline.

       expr	 This is an alias for eval.

       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.  Oth-
		 erwise, 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.

       eval	 evaluates its argument as an arithmetic  expression,  using  32-bit  arithmetic.
		 Operators include +, -, *, /, %, ^ (exponentiation); relationals; parentheses.

       len	 returns the number of characters in its argument.

       m4exit	 Immediately  exits  with  the return value specified by the first argument, 0 if

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

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

       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 inaccessi-

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

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

       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.

       popdef	 Restores the pushdef'd definition for each argument.

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

       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.

       spaste	 Similar to paste, except it ignores any errors.

       syscal	 Returns the return value from the last syscmd.

       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.

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

       B. W. Kernighan and D. M. Ritchie, The m4 Macro Processor

       An m4 command appeared in Version 6 AT&T UNIX.

       Ozan Yigit <oz@sis.yorku.ca>

3rd Berkeley Distribution		  April 14, 1994				    m4(1)
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