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M4(1P)                     POSIX Programmer's Manual                    M4(1P)

PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
       implementation of this interface may differ (consult the  corresponding
       Linux  manual page for details of Linux behavior), or the interface may
       not be implemented on Linux.
NAME
       m4 - macro processor (DEVELOPMENT)
SYNOPSIS
       m4 [-s][-D name[=val]]...[-U name]... file...
DESCRIPTION
       The m4 utility is a macro processor that shall read one  or  more  text
       files,  process  them according to their included macro statements, and
       write the results to standard output.
OPTIONS
       The m4  utility  shall  conform  to  the  Base  Definitions  volume  of
       IEEE Std 1003.1-2001,  Section  12.2, Utility Syntax Guidelines, except
       that the order of the -D and -U options shall be significant.
       The following options shall be supported:
       -s     Enable line synchronization  output  for  the  c99  preprocessor
              phase (that is, #line directives).
       -D  name[=val]
              Define name to val or to null if = val is omitted.
       -U  name
              Undefine name.

OPERANDS
       The following operand shall be supported:
       file   A  pathname of a text file to be processed. If no file is given,
              or if it is '-', the standard input shall be read.

STDIN
       The standard input shall be a text file that is used if no file operand
       is given, or if it is '-' .
INPUT FILES
       The input file named by the file operand shall be a text file.
ENVIRONMENT VARIABLES
       The following environment variables shall affect the execution of m4:
       LANG   Provide  a  default value for the internationalization variables
              that are unset or null. (See  the  Base  Definitions  volume  of
              IEEE Std 1003.1-2001,  Section  8.2,  Internationalization Vari-
              ables for the precedence of internationalization variables  used
              to determine the values of locale categories.)
       LC_ALL If  set  to a non-empty string value, override the values of all
              the other internationalization variables.
       LC_CTYPE
              Determine the locale for  the  interpretation  of  sequences  of
              bytes  of  text  data as characters (for example, single-byte as
              opposed to multi-byte characters in arguments and input files).
       LC_MESSAGES
              Determine the locale that should be used to  affect  the  format
              and contents of diagnostic messages written to standard error.
       NLSPATH
              Determine the location of message catalogs for the processing of
              LC_MESSAGES .

ASYNCHRONOUS EVENTS
       Default.
STDOUT
       The standard output shall be the same as the input files,  after  being
       processed for macro expansion.
STDERR
       The  standard  error shall be used to display strings with the errprint
       macro, macro tracing enabled by the traceon macro, the defined text for
       macros written by the dumpdef macro, or for diagnostic messages.
OUTPUT FILES
       None.
EXTENDED DESCRIPTION
       The  m4 utility shall compare each token from the input against the set
       of built-in and user-defined macros. If the token matches the name of a
       macro,  then  the token shall be replaced by the macro's defining text,
       if any, and rescanned for matching macro names. Once no portion of  the
       token matches the name of a macro, it shall be written to standard out-
       put. Macros may have arguments, in which case the  arguments  shall  be
       substituted into the defining text before it is rescanned.
       Macro calls have the form:

              name(arg1, arg2, ..., argn)
       Macro  names  shall  consist of letters, digits, and underscores, where
       the first character is not a digit. Tokens not of this form  shall  not
       be treated as macros.
       The application shall ensure that the left parenthesis immediately fol-
       lows the name of the macro. If a token matching the name of a macro  is
       not  followed  by  a  left  parenthesis, it is handled as a use of that
       macro without arguments.
       If a macro name is followed by a left parenthesis,  its  arguments  are
       the  comma-separated tokens between the left parenthesis and the match-
       ing right parenthesis. Unquoted <blank>s and <newline>s preceding  each
       argument  shall  be  ignored.  All other characters, including trailing
       <blank>s and <newline>s, are retained.  Commas  enclosed  between  left
       and right parenthesis characters do not delimit arguments.
       Arguments  are  positionally defined and referenced. The string "$1" in
       the defining text shall be replaced  by  the  first  argument.  Systems
       shall  support at least nine arguments; only the first nine can be ref-
       erenced, using the strings "$1" to "$9", inclusive. The string "$0"  is
       replaced with the name of the macro. The string "$#" is replaced by the
       number of arguments as a string. The string "$*" is replaced by a  list
       of  all  of  the  arguments,  separated  by commas.  The string "$@" is
       replaced by a list of all of the arguments  separated  by  commas,  and
       each  argument  is  quoted  using  the  current  left and right quoting
       strings.
       If fewer arguments are supplied than are in the macro  definition,  the
       omitted  arguments  are  taken  to  be null. It is not an error if more
       arguments are supplied than are in the macro definition.
       No special meaning is given to any characters enclosed between matching
       left  and right quoting strings, but the quoting strings are themselves
       discarded. By default, the left quoting  string  consists  of  a  grave
       accent ( '`' ) and the right quoting string consists of an acute accent
       ( '" ); see also the changequote macro.
       Comments are written but not  scanned  for  matching  macro  names;  by
       default, the begin-comment string consists of the number sign character
       and the end-comment string  consists  of  a  <newline>.  See  also  the
       changecom and dnl macros.
       The  m4  utility  shall  make  available the following built-in macros.
       They can be redefined, but once this is done the  original  meaning  is
       lost.  Their  values  shall  be  null  unless  otherwise stated. In the
       descriptions below, the term defining text refers to the value  of  the
       macro:  the  second  argument  to the define macro, among other things.
       Except for the first argument to the eval macro, all numeric  arguments
       to  built-in  macros shall be interpreted as decimal values. The string
       values produced as the defining text of the decr, divnum, incr,  index,
       len,  and sysval built-in macros shall be in the form of a decimal-con-
       stant as defined in the C language.
       changecom
              The changecom macro shall set the begin-comment and  end-comment
              strings.  With no arguments, the comment mechanism shall be dis-
              abled. With a single argument, that argument  shall  become  the
              begin-comment string and the <newline> shall become the end-com-
              ment string. With two arguments, the first argument shall become
              the  begin-comment  string  and the second argument shall become
              the end-comment string. Systems shall support comment strings of
              at least five characters.
       changequote
              The  changequote  macro  shall set the begin-quote and end-quote
              strings. With no arguments, the quote strings shall  be  set  to
              the  default  values (that is, `'). With a single argument, that
              argument shall become the begin-quote string and  the  <newline>
              shall become the end-quote string. With two arguments, the first
              argument shall become the  begin-quote  string  and  the  second
              argument  shall  become the end-quote string. Systems shall sup-
              port quote strings of at least five characters.
       decr   The defining text of the decr macro shall be its first  argument
              decremented  by  1.  It shall be an error to specify an argument
              containing any non-numeric characters.
       define The second argument shall become the defining text of the  macro
              whose name is the first argument.
       defn   The  defining text of the defn macro shall be the quoted defini-
              tion (using the current quoting strings) of its arguments.
       divert The m4 utility maintains nine temporary buffers, numbered  1  to
              9, inclusive. When the last of the input has been processed, any
              output that has been placed in these buffers shall be written to
              standard  output  in  buffer-numerical  order.  The divert macro
              shall divert future output to the buffer specified by its  argu-
              ment.  Specifying  no  argument or an argument of 0 shall resume
              the normal output process. Output diverted  to  a  stream  other
              than  0 to 9 shall be discarded. It shall be an error to specify
              an argument containing any non-numeric characters.
       divnum The defining text of the divnum macro shall be the number of the
              current output stream as a string.
       dnl    The  dnl macro shall cause m4 to discard all input characters up
              to and including the next <newline>.
       dumpdef
              The dumpdef macro shall write the defined text to standard error
              for  each  of the macros specified as arguments, or, if no argu-
              ments are specified, for all macros.
       errprint
              The errprint macro shall write its arguments to standard error.
       eval   The eval macro shall evaluate its first argument  as  an  arith-
              metic  expression,  using 32-bit signed integer arithmetic.  All
              of the C-language operators shall be supported, except for:

              []
              ->
              ++
              --
              (type)
              unary *
              sizeof,
              .
              ?:
              unary &
       and all assignment operators. It shall be an error to  specify  any  of
       these  operators. Precedence and associativity shall be as in the ISO C
       standard. Systems shall support octal and hexadecimal numbers as in the
       ISO C  standard. The second argument, if specified, shall set the radix
       for the result; the default is 10.  The third argument,  if  specified,
       sets  the  minimum number of digits in the result. It shall be an error
       to specify the second or  third  argument  containing  any  non-numeric
       characters.
       ifdef  If  the first argument to the ifdef macro is defined, the defin-
              ing text shall be the second argument. Otherwise,  the  defining
              text  shall  be  the  third  argument, if specified, or the null
              string, if not.
       ifelse The ifelse macro takes three or more arguments. If the first two
              arguments  compare  as  equal  strings (after macro expansion of
              both arguments), the defining text shall be the third  argument.
              If  the  first two arguments do not compare as equal strings and
              there are three arguments, the defining text shall be  null.  If
              the  first  two  arguments  do  not compare as equal strings and
              there are four or five arguments, the defining text shall be the
              fourth  argument.  If  the first two arguments do not compare as
              equal strings and there are six or  more  arguments,  the  first
              three  arguments shall be discarded and processing shall restart
              with the remaining arguments.
       include
              The defining text for the include macro shall be the contents of
              the  file  named  by the first argument. It shall be an error if
              the file cannot be read.
       incr   The defining text of the incr macro shall be its first  argument
              incremented  by  1.  It shall be an error to specify an argument
              containing any non-numeric characters.
       index  The defining text of the index macro shall be the first  charac-
              ter  position (as a string) in the first argument where a string
              matching the second argument begins (zero origin), or -1 if  the
              second argument does not occur.
       len    The  defining  text  of  the len macro shall be the length (as a
              string) of the first argument.
       m4exit Exit from the m4 utility. If the first argument is specified, it
              is  the  exit code. The default is zero. It shall be an error to
              specify an argument containing any non-numeric characters.
       m4wrap The first argument shall be processed when EOF  is  reached.  If
              the m4wrap macro is used multiple times, the arguments specified
              shall be processed in the order in which the m4wrap macros  were
              processed.
       maketemp
              The defining text shall be the first argument, with any trailing
              'X' characters replaced with the current process ID as a string.
       popdef The popdef macro shall delete  the  current  definition  of  its
              arguments,  replacing that definition with the previous one.  If
              there is no previous definition, the macro is undefined.
       pushdef
              The pushdef macro shall be equivalent to the define  macro  with
              the  exception that it shall preserve any current definition for
              future retrieval using the popdef macro.
       shift  The defining text for the shift macro shall be all of its  argu-
              ments except for the first one.
       sinclude
              The  sinclude  macro  shall  be equivalent to the include macro,
              except that it shall not be an error if the file  is  inaccessi-
              ble.
       substr The defining text for the substr macro shall be the substring of
              the first argument beginning at the zero-offset character  posi-
              tion  specified  by  the second argument. The third argument, if
              specified, shall be the number of characters to select;  if  not
              specified,  the characters from the starting point to the end of
              the first argument shall become the defining text. It shall  not
              be  an  error  to specify a starting point beyond the end of the
              first argument and the defining text shall be null. It shall  be
              an error to specify an argument containing any non-numeric char-
              acters.
       syscmd The syscmd macro shall interpret its first argument as  a  shell
              command  line.  The  defining text shall be the string result of
              that command. No output redirection shall be performed by the m4
              utility. The exit status value from the command can be retrieved
              using the sysval macro.
       sysval The defining text of the sysval macro shall be the exit value of
              the utility last invoked by the syscmd macro (as a string).
       traceon
              The  traceon macro shall enable tracing for the macros specified
              as arguments, or, if no arguments are specified, for all macros.
              The  trace  output  shall  be  written  to  standard error in an
              unspecified format.
       traceoff
              The traceoff macro shall disable tracing for the  macros  speci-
              fied  as  arguments,  or, if no arguments are specified, for all
              macros.
       translit
              The defining text of the translit macro shall be the first argu-
              ment  with  every  character  that occurs in the second argument
              replaced with the corresponding character from the  third  argu-
              ment.
       undefine
              The undefine macro shall delete all definitions (including those
              preserved using the pushdef macro) of the macros  named  by  its
              arguments.
       undivert
              The  undivert  macro shall cause immediate output of any text in
              temporary buffers named as arguments, or all  temporary  buffers
              if  no  arguments  are specified. Buffers can be undiverted into
              other temporary buffers. Undiverting shall discard the  contents
              of  the  temporary  buffer.  It  shall be an error to specify an
              argument containing any non-numeric characters.

EXIT STATUS
       The following exit values shall be returned:
        0     Successful completion.
       >0     An error occurred

       If the m4exit macro is used, the exit value can  be  specified  by  the
       input file.
CONSEQUENCES OF ERRORS
       Default.
       The following sections are informative.
APPLICATION USAGE
       The defn macro is useful for renaming macros, especially built-ins.
EXAMPLES
       If the file m4src contains the lines:

              The value of `VER' is "VER".
              ifdef(`VER', "VER" is defined to be VER., VER is not defined.)
              ifelse(VER, 1, "VER" is `VER'.)
              ifelse(VER, 2, "VER" is `VER'., "VER" is not 2.)
              end
       then the command

              m4 m4src
       or the command:

              m4 -U VER m4src
       produces the output:

              The value of VER is "VER".
              VER is not defined.

              VER is not 2.
              end
       The command:

              m4 -D VER m4src
       produces the output:

              The value of VER is "".
              VER is defined to be .

              VER is not 2.
              end
       The command:

              m4 -D VER=1 m4src
       produces the output:

              The value of VER is "1".
              VER is defined to be 1.
              VER is 1.
              VER is not 2.
              end
       The command:

              m4 -D VER=2 m4src

              produces the output:
              The value of VER is "2".
              VER is defined to be 2.

              VER is 2.
              end
RATIONALE
       None.
FUTURE DIRECTIONS
       None.
SEE ALSO
       c99
COPYRIGHT
       Portions  of  this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
       --  Portable  Operating  System  Interface (POSIX), The Open Group Base
       Specifications Issue 6, Copyright (C) 2001-2003  by  the  Institute  of
       Electrical  and  Electronics  Engineers, Inc and The Open Group. In the
       event of any discrepancy between this version and the original IEEE and
       The  Open Group Standard, the original IEEE and The Open Group Standard
       is the referee document. The original Standard can be  obtained  online
       at http://www.opengroup.org/unix/online.html .

IEEE/The Open Group                  2003                               M4(1P)