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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).  m4 reads from
     the standard input and writes the processed text 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
     parenthesis (`(').  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
     followed 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
     redefined, losing their original meaning.  Return values are null unless
     otherwise stated.

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

     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
                      arguments.  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 number of arguments; `$*' is replaced
                      by all arguments comma separated; `$@' is the same as
                      `$*' but all arguments are quoted against further

     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              Discards input characters up to and including the next

     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 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
                      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

     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
                      argument (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

     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
                      replacement string.  Usual substitution patterns apply:
                      an ampersand (`&') 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
                      definition on a stack for later retrieval by popdef.

     regexp           Finds a regular expression in a string.  If no further
                      arguments 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

     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 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

     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
                      arguments, 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

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

     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

     m4 follows the Single Unix 2 specification, 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
     current format of tracing is closely modeled on GNU-m4, to allow autoconf
     to work.

     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

     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

FreeBSD 11.0-PRERELEASE         April 17, 2002         FreeBSD 11.0-PRERELEASE


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