m4(1)                        UNIX Reference Manual                       m4(1)

NAME
     m4 - macro language processor

SYNOPSIS
     m4 [-Dname[=value]] [-Uname] [filename] ...

DESCRIPTION
     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).  Each of the ar-
     gument 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 sent to
     the standard output.

     Macro calls have the form name(argument1[, argument2, ...,] argumentN).

     There cannot be any space following the macro name and the open parenthe-
     ses '('.  If the macro name is not followed by an open parentheses it is
     processed with no arguments.

     Macro names consist of a leading alphabetic or underscore possibly fol-
     lowed by alphanumeric or underscore characters, therefore valid macro
     names match this pattern [a-zA-Z_][a-zA-Z0-9_]*.

     In arguments to macros, leading unquoted space, tab and newline charac-
     ters 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.

     The options are as follows:

     -Dname[=value]     Define the symbol name to have some value (or NULL).

     -Uname             Undefine the symbol name.

SYNTAX
     m4 provides the following built-in macros.  They may be redefined, losing
     their original meaning.  Return values are NULL unless otherwise stated.

     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 maximum length
                     for a comment marker is five characters.

     changequote     Defines the quote symbols to be the first and second ar-
                     guments.  Note, only the first character of each argument
                     is used.  If no arguments are given it restores the de-
                     fault 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 argu-
                     ment.  $0 is the name of the calling macro.  Undefined
                     arguments are replaced by a NULL string.  $# is replaced
                     by the number of arguments; $* is replaced by all argu-
                     ments comma separated; $@ is the same as $* but all argu-
                     ments 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 macros).

     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 discarded).

     divnum          Returns the current output queue number.

     dnl             Discard input characters up to and including the next
                     newline.

     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
                     stream.

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

     expr            This is an alias for eval.

     ifdef           If the macro named by the first argument is defined then
                     return the second argument, otherwise the third.  If
                     there is no third argument, the value is NULL.  The word
                     `unix' is predefined.

     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 ar-
                     guments 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
                     argument.  Include 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 ar-
                     gument (e.g., index(the quick brown fox jumped, fox) re-
                     turns 16).  If the second argument is not found index re-
                     turns -1.

     len             Returns the number of characters in the first argument.
                     Extra 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, usu-
                     ally for cleanup purposes (e.g., m4wrap("cleanup(temp-
                     file)") causes the macro cleanup to 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
                     argument without any macro processing.  Aborts with an
                     error message if the file cannot be included.

     popdef          Restores the pushdef'ed definition for each argument.

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

     shift           Returns all but the first argument, the remaining argu-
                     ments 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
                     specified 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-
                     turned.

     sysval          Returns the return value from the last syscmd.

     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 macro specified by the
                     first argument.

     undivert        Flushes the named output queues (or all queues if no ar-
                     guments).

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

AUTHORS
     Ozan Yigit <oz@sis.yorku.ca> and
     Richard A. O'Keefe <ok@goanna.cs.rmit.OZ.AU>

BSD Experimental               January 26, 1993                              1