M4(1)							      General Commands Manual							     M4(1)

NAME

       m4 - macro processor

SYNOPSIS

       m4 [ files ]

DESCRIPTION

       M4  is  a macro processor intended as a front end for Ratfor, C, and other languages.  Each of the argument files is processed in order; if
       there are no arguments, or if an argument is `-', the standard input is read.  The processed text is written on the standard output.

       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  argu-
       ments.	Leading  unquoted  blanks, tabs, and newlines are ignored while collecting arguments.  Potential macro names consist of alphabetic
       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 nor-
       mally during the collection of the arguments, 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 collection, the value of the macro is  pushed  back  onto	the  input
       stream and rescanned.

       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.  The word unix is predefined on UNIX versions of m4.

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

       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 (digit-string) 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 newline.

       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.

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

       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.

       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 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.

       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.

SEE ALSO

       B. W. Kernighan and D. M. Ritchie, The M4 Macro Processor

																	     M4(1)