 @@ -1,519 +1,519 @@
-.\"	$NetBSD: m4.1,v 1.28 2020/06/25 02:54:50 uwe Exp $
+.\"	$NetBSD: m4.1,v 1.29 2020/06/25 02:58:16 uwe Exp $
 .\"	@(#) $OpenBSD: m4.1,v 1.56 2009/10/14 17:19:47 sthen Exp $
 .\"
 .\" Copyright (c) 1989, 1993
 .\"	The Regents of the University of California.  All rights reserved.
 .\"
 .\" This code is derived from software contributed to Berkeley by
 .\" Ozan Yigit at York University.
 .\"
 .\" Redistribution and use in source and binary forms, with or without
 .\" modification, are permitted provided that the following conditions
 .\" are met:
 .\" 1. Redistributions of source code must retain the above copyright
 .\"    notice, this list of conditions and the following disclaimer.
 .\" 2. Redistributions in binary form must reproduce the above copyright
 .\"    notice, this list of conditions and the following disclaimer in the
 .\"    documentation and/or other materials provided with the distribution.
 .\" 3. Neither the name of the University nor the names of its contributors
 .\"    may be used to endorse or promote products derived from this software
 .\"    without specific prior written permission.
 .\"
 .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 .\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.Dd January 16, 2015
+.Dd June 25 16, 2020
 .Dt M4 1
 .Os
 .Sh NAME
 .Nm m4
 .Nd macro language processor
 .Sh SYNOPSIS
 .Nm m4
 .Op Fl EGgiPQsv
 .Oo
 .Sm off
 .Fl D Ar name Op No = Ar value
 .Sm on
 .Oc
 .Op Fl d Ar flags
 .Op Fl F Ar filename
 .Op Fl I Ar dirname
 .Op Fl L Ar number
 .Op Fl o Ar filename
 .Op Fl R Ar filename
 .Op Fl t Ar macro
 .Op Fl U Ns Ar name
 .Op Ar
 .Sh DESCRIPTION
 The
 .Nm 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).
 If no input files are given,
 .Nm m4
 reads from the standard input,
 otherwise files specified on the command line are
 processed in the given order.
 Input files can be regular files, files in the m4 include paths, or a
 single dash
 .Pq Sq - ,
 denoting standard input.
 .Nm m4
 writes
 the processed text to the standard output, unless told otherwise.
 .Pp
 Macro calls have the form name(argument1[, argument2, ..., argumentN]).
 .Pp
 There cannot be any space following the macro name and the open
 parenthesis
 .Sq \&( .
 If the macro name is not followed by an open
 parenthesis it is processed with no arguments.
 .Pp
 Macro names consist of a leading alphabetic or underscore
 possibly followed by alphanumeric or underscore characters, e.g.,
 valid macro names match the pattern
 .Dq [a-zA-Z_][a-zA-Z0-9_]* .
 .Pp
 In arguments to macros, leading unquoted space, tab, and newline
 .Pq Sq \en
 characters are ignored.
 To quote strings, use left and right single quotes
 .Po e.g.,\ \&
 .Sq "\ this is a string with a leading space"
 .Pc .
 You can change the quote characters with the
 .Ic changequote
 built-in macro.
 .Pp
 Most built-ins don't make any sense without arguments, and hence are not
 recognized as special when not followed by an open parenthesis.
 .Pp
 The options are as follows:
 .Bl -tag -width Ds
 .It Fl D , Fl Fl define Ar name Ns Op Pf = Ns Ar value
 Define the symbol
 .Ar name
 to have some value (or
 .Dv NULL ) .
 .It Fl d , Fl Fl debug Ar "flags"
 Set trace flags.
 .Ar flags
 may hold the following:
 .Bl -tag -width Ds
 .It Ar a
 print macro arguments.
 .It Ar c
 print macro expansion over several lines.
 .It Ar e
 print result of macro expansion.
 .It Ar f
 print filename location.
 .It Ar l
 print line number.
 .It Ar q
 quote arguments and expansion with the current quotes.
 .It Ar t
 start with all macros traced.
 .It Ar x
 number macro expansions.
 .It Ar V
 turn on all options.
 .El
 .Pp
 By default, trace is set to
 .Qq eq .
 .It Fl E , Fl Fl fatal-warnings
 Warnings make
 .Nm
 exit.
 .It Fl F , Fl Fl freeze-state Ar filename
 Save the input state to
 .Ar filename .
 .It Fl G , Fl Fl traditional
 Disable GNU-m4 extensions.
 .It Fl g , Fl Fl gnu
 Activate GNU-m4 compatibility mode.
 In this mode, translit handles simple character
 ranges (e.g., a-z), regular expressions mimic emacs behavior,
 multiple m4wrap calls are handled as a stack,
 the number of diversions is unlimited,
 empty names for macro definitions are allowed,
 and eval understands
 .Sq 0rbase:value
 numbers.
 .It Fl Fl help
 Print help message and exit.
 .It Fl I , Fl Fl include Ar "dirname"
 Add directory
 .Ar dirname
 to the include path.
 .It Fl i , Fl Fl interactive
 Set unbuffered output, disable tty signals.
 .It Fl L , Fl Fl nesting-limit
 Set the nesting limit in macro expansions.
 This is unimplemented and unlimited.
 .It Fl o , Fl Fl error-output Ar filename
 Send trace output to
 .Ar filename .
 .It Fl P , Fl Fl prefix-builtins
 Prefix all built-in macros with
 .Sq m4_ .
 For example, instead of writing
 .Ic define ,
 use
 .Ic m4_define .
 .It Fl Q , Fl Fl quiet , Fl Fl silent
 Don't print warnings.
 .It Fl R , Fl Fl reload-state Ar filename
 Reload a previously saved state from
 .Ar filename .
 .It Fl s , Fl Fl synclines
 Output line synchronization directives, suitable for
 .Xr cpp 1 .
 .It Fl t , Fl Fl trace Ar macro
 Turn tracing on for
 .Ar macro .
 .It Fl U , Fl Fl undefine Ar "name"
 Undefine the symbol
 .Ar name .
 .It Fl v , Fl Fl version
 Print the version and exit.
 .El
 .Sh SYNTAX
 .Nm m4
 provides the following built-in macros.
 They may be redefined, losing their original meaning.
 Return values are null unless otherwise stated.
 .Bl -tag -width changequote
 .It Fn builtin name
 Calls a built-in by its
 .Fa name ,
 overriding possible redefinitions.
 .It Fn changecom startcomment endcomment
 Changes the start comment and end comment sequences.
 Comment sequences may be up to five characters long.
 The default values are the hash sign
 and the newline character.
 .Bd -literal -offset indent
 # This is a comment
 .Ed
 .Pp
 With no arguments, comments are turned off.
 With one single argument, the end comment sequence is set
 to the newline character.
 .It Fn changequote beginquote endquote
 Defines the open quote and close quote sequences.
 Quote sequences may be up to five characters long.
 The default values are the backquote character and the quote
 character.
 .Bd -literal -offset indent
 `Here is a quoted string'
 .Ed
 .Pp
 With no arguments, the default quotes are restored.
 With one single argument, the close quote sequence is set
 to the newline character.
 .It Fn decr arg
 Decrements the argument
 .Fa arg
 by 1.
 The argument
 .Fa arg
 must be a valid numeric string.
 .It Fn define name value
 Define a new macro named by the first argument
 .Fa name
 to have the
 value of the second argument
 .Fa value .
 Each occurrence of
 .Sq $n
 (where
 .Ar n
 is 0 through 9) is replaced by the
 .Ar n Ns 'th
 argument.
 .Sq $0
 is the name of the calling macro.
 Undefined arguments are replaced by a null string.
 .Sq $#
 is replaced by the number of arguments;
 .Sq $*
 is replaced by all arguments comma separated;
 .Sq $@
 is the same as
 .Sq $*
 but all arguments are quoted against further expansion.
 .It Fn defn name ...
 Returns the quoted definition for each argument.
 This can be used to rename
 macro definitions (even for built-in macros).
 .It Fn divert num
 There are 10 output queues (numbered 0-9).
 At the end of processing
 .Nm 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).
 .It Ic divnum
 Returns the current output queue number.
 .It Ic dnl
 Discard input characters up to and including the next newline.
 .It Fn dumpdef name ...
 Prints the names and definitions for the named items, or for everything
 if no arguments are passed.
 .It Fn errprint msg
 Prints the first argument on the standard error output stream.
 .It Fn esyscmd cmd
 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
 .Nm m4 .
 .It Fn eval expr[,radix[,minimum]]
 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 optional second argument
 .Fa radix
 specifies the radix for the result and the optional third argument
 .Fa minimum
 specifies the minimum number of digits in the result.
 .It Fn expr expr
 This is an alias for
 .Ic eval .
 .It Fn format formatstring arg1 ...
 Returns
 .Fa formatstring
 with escape sequences substituted with
 .Fa arg1
 and following arguments, in a way similar to
 .Xr printf 3 .
 This built-in is only available in GNU-m4 compatibility mode, and the only
 parameters implemented are there for autoconf compatibility:
 left-padding flag, an optional field width, a maximum field width,
 *-specified field widths, and the %s and %c data type.
 .It Fn ifdef name yes no
 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
 .Dv NULL .
 The word
 .Qq unix
 is predefined.
 .It Fn ifelse a b yes ...
 If the first argument
 .Fa a
 matches the second argument
 .Fa b
 then
 .Fn ifelse
 returns
 the third argument
 .Fa yes .
 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
 .Dv NULL
 is returned if no other matches were found.
 .It Fn include name
 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
 .Fl I
 on the command line, then the environment variable
 .Ev M4PATH ,
 as a colon-separated list of directories.
 Include aborts with an error message if the file cannot be included.
 .It Fn incr arg
 Increments the argument by 1.
 The argument must be a valid numeric string.
 .It Fn index string substring
 Returns the index of the second argument in the first argument (e.g.,
 .Ic index(the quick brown fox jumped, fox)
 returns 16).
 If the second
 argument is not found index returns \-1.
 .It Fn indir macro arg1 ...
 Indirectly calls the macro whose name is passed as the first argument,
 with the remaining arguments passed as first, ... arguments.
 .It Fn len arg
 Returns the number of characters in the first argument.
 Extra arguments
 are ignored.
 .It Fn m4exit code
 Immediately exits with the return value specified by the first argument,
 if none.
 .It Fn m4wrap todo
 Allows you to define what happens at the final
 .Dv EOF ,
 usually for cleanup purposes (e.g.,
 .Ic m4wrap("cleanup(tempfile)")
 causes the macro cleanup to be
 invoked after all other processing is done).
 .Pp
 Multiple calls to
 .Fn m4wrap
 get inserted in sequence at the final
 .Dv EOF .
 .It Fn maketemp template
 Invokes
 .Xr mkstemp 3
 on the first argument, and returns the modified string.
 This can be used to create unique
 temporary file names.
 .It Fn paste file
 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.
 .It Fn patsubst string regexp replacement
 Substitutes a regular expression in a string with a replacement string.
 Usual substitution patterns apply: an ampersand
 .Pq Sq \&&
 is replaced by the string matching the regular expression.
 The string
 .Sq \e# ,
 where
 .Sq #
 is a digit, is replaced by the corresponding back-reference.
 .It Fn popdef arg ...
 Restores the
 .Ic pushdef Ns ed
 definition for each argument.
 .It Fn pushdef macro def
 Takes the same arguments as
 .Ic define ,
 but it saves the definition on a
 stack for later retrieval by
 .Fn popdef .
 .It Fn regexp string regexp replacement
 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.
 .It Fn shift arg1 ...
 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.
 .It Fn sinclude file
 Similar to
 .Ic include ,
 except it ignores any errors.
 .It Fn spaste file
 Similar to
 .Fn paste ,
 except it ignores any errors.
 .It Fn substr string offset length
 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.
 .It Fn syscmd cmd
 Passes the first argument to the shell.
 Nothing is returned.
 .It Ic sysval
 Returns the return value from the last
 .Ic syscmd .
 .It Fn traceon arg ...
 Enables tracing of macro expansions for the given arguments, or for all
 macros if no argument is given.
 .It Fn traceoff arg ...
 Disables tracing of macro expansions for the given arguments, or for all
 macros if no argument is given.
 .It Fn translit string mapfrom mapto
 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
 .Xr tr 1
 style abbreviations.
 .It Fn undefine name1 ...
 Removes the definition for the macros specified by its arguments.
 .It Fn undivert arg ...
 Flushes the named output queues (or all queues if no arguments).
 .It Ic unix
 A pre-defined macro for testing the OS platform.
 .It Ic __line__
 Returns the current file's line number.
 .It Ic __file__
 Returns the current file's name.
 .El
 .Sh STANDARDS
 The
 .Nm
 utility is compliant with the
 .St -p1003.1-2008
 specification.
 .Pp
 The flags
 .Op Fl dgIot
 and the macros
 .Ic builtin ,
 .Ic esyscmd ,
 .Ic expr ,
 .Ic format ,
 .Ic indir ,
 .Ic paste ,
 .Ic patsubst ,
 .Ic regexp ,
 .Ic spaste ,
 .Ic unix ,
 .Ic __line__ ,
 and
 .Ic __file__
 are extensions to that specification.
 .Pp
 The output format of tracing and of
 .Ic dumpdef
 are not specified in any standard,
 are likely to change and should not be relied upon.
 The current format of tracing is closely modelled on
 .Nm gnu-m4 ,
 to allow
 .Nm autoconf
 to work.
 .Pp
 The built-ins
 .Ic pushdef
 and
 .Ic popdef
 handle macro definitions as a stack.
 However,
 .Ic define
 interacts with the stack in an undefined way.
 In this implementation,
 .Ic define
 replaces the top-most definition only.
 Other implementations may erase all definitions on the stack instead.
 .Pp
 All built-ins do expand without arguments in many other
 .Nm m4 .
 .Pp
 Many other
 .Nm
 have dire size limitations with respect to buffer sizes.
 .Sh AUTHORS
 .An -nosplit
 .An Ozan Yigit Aq Mt oz@sis.yorku.ca
 and
 .An Richard A. O'Keefe Aq Mt ok@goanna.cs.rmit.OZ.AU .
 .Pp
 GNU-m4 compatibility extensions by
 .An Marc Espie Aq Mt espie@cvs.openbsd.org .