m4(1)							      General Commands Manual							     m4(1)

Name
       m4 - macro processor

Syntax
       m4 [options] [files]

Description
       The  macro  processor  is 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 hypen (-), the standard input is read.  The processed text is written on the standard output.

Options
       The options and their effects are as follows:

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

       -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 bytes.

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

       -Dname[=val]
	      Defines name to val or to null in val's absence.

       -Uname undefines name.

       Macro calls have the following form:
       name(arg1,arg2, . . . , argn)

       The left parenthesis ( ( ) must immediately follow the name of the macro.  If a defined macro name is not followed by a	left  parenthesis,
       it is deemed to have no arguments.

       Leading	unquoted blanks, tabs, and new lines 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.

       The  makes available the following built-in macros.  They may be redefined, but once this is done the original meaning is lost.	Their val-
       ues 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; miss-
			   ing 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 is defined, the value is the second argument, otherwise the third.	If there is no third argu-
			   ment, the value is null.  The word unix is predefined on UNIX versions of

       changequote	   Change quote characters to the first and second arguments.  The changequote without	arguments  restores  the  original
			   values (that is, `').

       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		   The	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 new line.

       ifelse		   has three or more arguments.  If the first argument is the same string as the second, then the value is the third argu-
			   ment.  If not, and if there are more than four arguments, the process is repeated with arguments 4, 5, 6 and 7.  Other-
			   wise, 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 +, -, *, /, %, ^ (expo-
			   nentiation), 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.

       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.

       shift		   is an unimplemented macro.  Using shift generates an error message.

       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.

       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		   argument 1 will be pushed back at final EOF.  For example:
			   m4wrap(`cleanup()')

       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
       "The M4 Macro Processor," ULTRIX Supplementary Documents Vol. II:Programmer

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