M4(1)                   NetBSD General Commands Manual                   M4(1)

NAME
     m4 -- macro language processor

SYNOPSIS
     m4 [-Pg] [-Dname[=value]] [-I dirname] [-Uname] [-d flags] [-o trfile]
        [-t name]

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).  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 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 don't make any sense without arguments, and hence are not
     recognized as special when not followed by an open parenthesis.

     The options are as follows:

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

     -I dirname         Add directory dirname to the include path.

     -P                 Prefixes all m4 builtin macros with the string
                        ``m4_''.  This changes the macro names ``dnl'' to
                        ``m4_dnl'', ``index'' to ``m4_index'', and so forth.

     -Uname             Undefine the symbol name.

     -d flags           Set trace flags.  flags 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".

     -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 behavior,
                        and the number of diversions is unlimited.

     -o trfile          Specify the tracing output file for -t; tracing
                        defaults to printing to stderr.

     -t macro           Turn tracing on for macro.

SYNTAX
     m4 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 redefi-
                     nitions.

     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
                     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 fur-
                     ther 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.

     esyscmd         Pass 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, 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
                     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.
                     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
                     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, ... 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, usu-
                     ally 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
                     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 def-
                     inition 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
                     replaced.

     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
                     returned.

     sysval          Returns the return value from the last syscmd.

     traceon         Enables tracing of macro expansions for the given argu-
                     ments, 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 macro specified by the
                     first argument.

     undivert        Flushes the named output queues (or all queues if no
                     arguments).

     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.

STANDARDS
     The m4 utility is expected to be a superset of the X/Open Commands and
     Utilities Issue 5 (``XCU5'') specification, and includes some extensions
     also present in GNU m4.

     The -s option (cpp(1)'s #line directives) is currently not supported.
     Flags -I, -d, -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 modelled on GNU m4, to allow autoconf
     to work.

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

     All builtins do expand without arguments in many other m4.

AUTHORS
     Ozan Yigit <oz@sis.yorku.ca> and Richard A. O'Keefe (ok@cs.rmit.edu.au).
     GNU-m4 compatibility extensions by Marc Espie <espie@cvs.openbsd.org>.

NetBSD 5.0_STABLE              January 26, 1993              NetBSD 5.0_STABLE
