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M4(1)                   FreeBSD General Commands Manual                  M4(1)

     m4 -- macro language processor

     m4 [-d flags] [-t name] [-gs] [-D name[=value]] [-U name] [-I dirname]
        [file ...]

     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).  The m4 utility
     reads from the standard input and writes the processed text to the stan-
     dard output.

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

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

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

     In arguments to macros, leading unquoted space, tab, and newline (`\n')
     characters 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.

     Most built-ins do not make any sense without arguments, and hence are not
     recognized as special when not followed by an open parenthesis.

     The options are as follows:

     -s      Emit #line directives for cpp(1).

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

     -U name
             Undefine the symbol name.

     -I dirname
             Add directory dirname to the include path.

     -d flags
             Set trace flags.  The flags argument may hold the following:

             a       print macro arguments
             c       print macro expansion over several lines
             e       print result of macro expansion
             f       print filename location
             l       print line number
             q       quote arguments and expansion with the current quotes
             t       start with all macros traced
             x       number macro expansions
             V       turn on all options

             By default, trace is set to eq.

     -t macro
             Turn tracing on for macro.

     -g      Activate GNU-m4 compatibility mode.  In this mode, changequote
             with two empty parameters deactivates quotes, translit handles
             simple character ranges (e.g., a-z), regular expressions mimic
             emacs(1) behavior, and the number of diversions is unlimited.

     The m4 utility provides the following built-in macros.  They may be rede-
     fined, losing their original meaning.  Return values are null unless oth-
     erwise stated.

     builtin      Calls a built-in by its name, overriding possible redefini-

     changecom    Changes the start and end comment sequences.  The default is
                  the pound sign (`#') and the newline character.  With no
                  arguments, the comment sequence is reset to the default, in
                  GNU m4 mode, 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 argu-
                  ments.  The symbols may be up to five characters long.  If
                  no arguments are given it restores the default 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 argument.
                  `$0' is the name of the calling macro.  Undefined arguments
                  are replaced by a null string.  `$#' is replaced by the num-
                  ber of arguments; `$*' is replaced by all arguments comma
                  separated; `$@' is the same as `$*' but all arguments 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

     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

     divnum       Returns the current output queue number.

     dnl          Discards input characters up to and including the next new-

     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

     esyscmd      Passes its first argument to a shell and returns the shell's
                  standard output.  Note that the shell shares its standard
                  input and standard error with m4.

     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, decimal,
                  and hexadecimal numbers as in C.  The second argument (if
                  any) specifies the radix for the result, and the third argu-
                  ment (if any) specifies the minimum number of digits in the

     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

     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 arguments
                  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.  If the file is not found as is, look through the
                  include path: first the directories specified with -I on the
                  command line, then the environment variable M4PATH, as a
                  colon-separated list of directories.  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 argu-
                  ment (e.g., index(the quick brown fox jumped, fox) returns
                  16).  If the second argument is not found, index returns -1.

     indir        Indirectly calls the macro whose name is passed as the first
                  arguments, with the remaining arguments passed as first,
                  etc. arguments.

     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, usually
                  for cleanup purposes (e.g., m4wrap(cleanup(tempfile)) causes
                  the macro cleanup to be 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.

     patsubst     Substitutes a regular expression in a string with a replace-
                  ment string.  Usual substitution patterns apply: an amper-
                  sand (`&') is replaced by the string matching the regular
                  expression.  The string `\#', where # is a digit, is
                  replaced by the corresponding back-reference.

     popdef       Restores the pushdefed definition for each argument.

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

     regexp       Finds a regular expression in a string.  If no further argu-
                  ments are given, it returns the first match position or -1
                  if no match.  If a third argument is provided, it returns
                  the replacement string, with sub-patterns replaced.

     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.

     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 spec-
                  ified 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

     sysval       Returns the return value from the last syscmd.

     traceon      Enables tracing of macro expansions for the given arguments,
                  or for all macros if no argument is given.

     traceoff     Disables tracing of macro expansions for the given argu-
                  ments, or for all macros if no argument is given.

     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 macros specified by its argu-

     undivert     Flushes the named output queues (or all queues if no argu-

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

     __line__     Returns the current file's line number.

     __file__     Returns the current file's name.

     The m4 utility exits 0 on success, and >0 if an error occurs.

     The m4exit macro may be used to change the exit status from the input

     The m4 utility follows the Version 2 of the Single UNIX Specification
     (``SUSv2''), along with a few extensions taken from GNU-m4.  Flags -I,
     -d, and -t are non-standard.

     The output format of tracing and of dumpdef are not specified in any
     standard, are likely to change and should not be relied upon.  The cur-
     rent format of tracing is closely modeled on GNU-m4, to allow autoconf to

     For portability, one should not use the macros builtin, esyscmd, expr,
     indir, paste, patsubst, regexp, spaste, unix, __line__, and __file__.

     All built-ins do expand without arguments in many other m4 implementa-

     Many other m4 implementations have dire size limitations with respect to
     buffer sizes.

     The m4 utility conforms to IEEE Std 1003.1-2001 (``POSIX.1'').

     An m4 command appeared in PWB UNIX.

     Ozan Yigit <> and Richard A. O'Keefe
     <>.  GNU-m4 compatibility extensions by Marc Espie

     The m4 utility does not recognize multibyte characters.

FreeBSD 6.2                      July 3, 2004                      FreeBSD 6.2


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