415 lines
11 KiB
Groff
415 lines
11 KiB
Groff
.\" @(#) $OpenBSD: m4.1,v 1.24 2002/04/18 18:57:23 espie Exp $
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.\" $FreeBSD$
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.\"
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.Dd April 17, 2002
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.Dt M4 1
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.Os
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.Sh NAME
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.Nm m4
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.Nd macro language processor
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.Sh SYNOPSIS
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.Nm
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.Op Fl d Ar flags
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.Op Fl t Ar name
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.Op Fl gs
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.Op Fl D Ar name Ns Op = Ns Ar value
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.Op Fl U Ar name
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.Op Fl I Ar dirname
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.Op Ar
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.Sh DESCRIPTION
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The
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.Nm
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utility is a macro processor that can be used as a front end to any
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language (e.g., C, ratfor, fortran, lex, and yacc).
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.Nm
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reads from the standard input and writes
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the processed text to the standard output.
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.Pp
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Macro calls have the form
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.Ic name Ns Pq Ar argument1 Ns Op , Ar argument2 , ... , argumentN .
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.Pp
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There cannot be any space following the macro name and the open
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parenthesis
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.Pq Ql \&( .
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If the macro name is not followed by an open
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parenthesis it is processed with no arguments.
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.Pp
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Macro names consist of a leading alphabetic or underscore
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possibly followed by alphanumeric or underscore characters, e.g.,
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valid macro names match the pattern
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.Dq Li [a-zA-Z_][a-zA-Z0-9_]* .
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.Pp
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In arguments to macros, leading unquoted space, tab, and newline
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.Pq Ql \en
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characters are ignored.
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To quote strings, use left and right single
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quotes (e.g.,
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.Sq "\ this is a string with a leading space" ) .
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You can change the quote characters with the
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.Ic changequote
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built-in macro.
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.Pp
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Most built-ins do not make any sense without arguments, and hence are not
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recognized as special when not followed by an open parenthesis.
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.Pp
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The options are as follows:
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.Bl -tag -width indent
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.It Fl s
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Emit
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.Ic #line
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directives for
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.Xr cpp 1 .
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.It Fl D Ar name Ns Op = Ns Ar value
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Define the symbol
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.Ar name
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to have some value (or
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.Dv NULL ) .
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.It Fl U Ar name
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Undefine the symbol
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.Ar name .
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.It Fl I Ar dirname
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Add directory
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.Ar dirname
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to the include path.
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.It Fl d Ar flags
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Set trace flags.
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The
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.Ar flags
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argument may hold the following:
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.Pp
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.Bl -tag -width indent -compact
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.It Cm a
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print macro arguments
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.It Cm c
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print macro expansion over several lines
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.It Cm e
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print result of macro expansion
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.It Cm f
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print filename location
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.It Cm l
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print line number
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.It Cm q
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quote arguments and expansion with the current quotes
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.It Cm t
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start with all macros traced
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.It Cm x
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number macro expansions
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.It Cm V
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turn on all options
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.El
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.Pp
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By default, trace is set to
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.Cm eq .
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.It Fl t Ar macro
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Turn tracing on for
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.Ar macro .
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.It Fl g
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Activate GNU-m4 compatibility mode.
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In this mode,
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.Ic changequote
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with two empty parameters deactivates quotes,
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.Ic translit
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handles simple character ranges (e.g.,
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.Li a-z ) ,
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regular expressions mimic
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.Xr emacs 1
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behavior,
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and the number of diversions is unlimited.
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.El
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.Sh SYNTAX
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The
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.Nm
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utility provides the following built-in macros.
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They may be redefined, losing their original meaning.
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Return values are null unless otherwise stated.
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.Bl -tag -width ".Ic changequote"
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.It Ic builtin
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Calls a built-in by its name, overriding possible redefinitions.
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.It Ic changecom
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Changes the start and end comment sequences.
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The default is the pound sign
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.Pq Ql #
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and the newline character.
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With no arguments, the comment sequence is reset to the default,
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in GNU
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.Nm
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mode, comments are turned off.
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The maximum length for a comment marker is five characters.
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.It Ic changequote
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Defines the quote symbols to be the first and second arguments.
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The symbols may be up to five characters long.
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If no arguments are
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given it restores the default open and close single quotes.
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.It Ic decr
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Decrements the argument by 1.
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The argument must be a valid numeric string.
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.It Ic define
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Define a new macro named by the first argument to have the
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value of the second argument.
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Each occurrence of
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.Sq Li $ Ns Ar n
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(where
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.Ar n
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is 0 through 9) is replaced by the
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.Ar n Ns 'th
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argument.
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.Ql $0
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is the name of the calling macro.
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Undefined arguments are replaced by a null string.
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.Ql $#
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is replaced by the number of arguments;
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.Ql $*
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is replaced by all arguments comma separated;
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.Ql $@
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is the same as
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.Ql $*
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but all arguments are quoted against further expansion.
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.It Ic defn
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Returns the quoted definition for each argument.
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This can be used to rename
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macro definitions (even for built-in macros).
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.It Ic divert
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There are 10 output queues (numbered 0-9).
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At the end of processing
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.Nm
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concatenates all the queues in numerical order to produce the
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final output.
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Initially the output queue is 0.
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The
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.Ic divert
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macro allows you to select a new output queue (an invalid argument
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passed to
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.Ic divert
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causes output to be discarded).
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.It Ic divnum
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Returns the current output queue number.
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.It Ic dnl
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Discards input characters up to and including the next newline.
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.It Ic dumpdef
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Prints the names and definitions for the named items, or for everything
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if no arguments are passed.
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.It Ic errprint
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Prints the first argument on the standard error output stream.
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.It Ic esyscmd
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Passes its first argument to a shell and returns the shell's standard output.
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Note that the shell shares its standard input and standard error with
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.Nm .
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.It Ic eval
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Computes the first argument as an arithmetic expression using 32-bit
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arithmetic.
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Operators are the standard C ternary, arithmetic, logical,
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shift, relational, bitwise, and parentheses operators.
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You can specify
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octal, decimal, and hexadecimal numbers as in C.
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The second argument (if any)
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specifies the radix for the result, and the third argument (if any)
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specifies the minimum number of digits in the result.
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.It Ic expr
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This is an alias for
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.Ic eval .
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.It Ic ifdef
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If the macro named by the first argument is defined then return the second
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argument, otherwise the third.
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If there is no third argument, the value is
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.Dv NULL .
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The word
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.Ic unix
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is predefined.
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.It Ic ifelse
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If the first argument matches the second argument then
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.Ic ifelse
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returns
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the third argument.
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If the match fails, the three arguments are
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discarded and the next three arguments are used until there is
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zero or one arguments left, either this last argument or
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.Dv NULL
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is returned if no other matches were found.
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.It Ic include
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Returns the contents of the file specified in the first argument.
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If the file is not found as is, look through the include path:
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first the directories specified with
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.Fl I
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on the command line, then the environment variable
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.Ev M4PATH ,
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as a colon-separated list of directories.
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Aborts with an error message if the file cannot be included.
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.It Ic incr
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Increments the argument by 1.
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The argument must be a valid numeric string.
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.It Ic index
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Returns the index of the second argument in the first argument (e.g.,
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.Fn index "the quick brown fox jumped" fox
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returns 16).
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If the second
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argument is not found,
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.Ic index
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returns \-1.
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.It Ic indir
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Indirectly calls the macro whose name is passed as the first arguments,
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with the remaining arguments passed as first, etc. arguments.
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.It Ic len
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Returns the number of characters in the first argument.
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Extra arguments
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are ignored.
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.It Ic m4exit
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Immediately exits with the return value specified by the first argument,
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0 if none.
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.It Ic m4wrap
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Allows you to define what happens at the final
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.Dv EOF ,
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usually for cleanup purposes (e.g.,
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.Fn m4wrap cleanup(tempfile)
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causes the macro
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.Ic cleanup
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to be
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invoked after all other processing is done).
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.It Ic maketemp
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Translates the string
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.Dq Li XXXXX
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in the first argument with the current process
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ID leaving other characters alone.
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This can be used to create unique
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temporary file names.
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.It Ic paste
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Includes the contents of the file specified by the first argument without
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any macro processing.
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Aborts with an error message if the file cannot be
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included.
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.It Ic patsubst
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Substitutes a regular expression in a string with a replacement string.
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Usual substitution patterns apply: an ampersand
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.Pq Ql &
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is replaced by the string matching the regular expression.
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The string
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.Sq \e Ns Ar # ,
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where
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.Ar #
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is a digit, is replaced by the corresponding back-reference.
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.It Ic popdef
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Restores the
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.Ic pushdef Ns ed
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definition for each argument.
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.It Ic pushdef
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Takes the same arguments as
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.Ic define ,
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but it saves the definition on a
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stack for later retrieval by
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.Ic popdef .
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.It Ic regexp
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Finds a regular expression in a string.
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If no further arguments are given,
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it returns the first match position or \-1 if no match.
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If a third argument
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is provided, it returns the replacement string, with sub-patterns replaced.
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.It Ic shift
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Returns all but the first argument, the remaining arguments are
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quoted and pushed back with commas in between.
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The quoting
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nullifies the effect of the extra scan that will subsequently be
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performed.
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.It Ic sinclude
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Similar to
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.Ic include ,
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except it ignores any errors.
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.It Ic spaste
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Similar to
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.Ic paste ,
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except it ignores any errors.
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.It Ic substr
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Returns a substring of the first argument starting at the offset specified
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by the second argument and the length specified by the third argument.
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If no third argument is present it returns the rest of the string.
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.It Ic syscmd
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Passes the first argument to the shell.
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Nothing is returned.
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.It Ic sysval
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Returns the return value from the last
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.Ic syscmd .
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.It Ic traceon
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Enables tracing of macro expansions for the given arguments, or for all
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macros if no argument is given.
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.It Ic traceoff
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Disables tracing of macro expansions for the given arguments, or for all
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macros if no argument is given.
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.It Ic translit
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Transliterate the characters in the first argument from the set
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given by the second argument to the set given by the third.
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You cannot use
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.Xr tr 1
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style abbreviations.
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.It Ic undefine
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Removes the definition for the macros specified by its arguments.
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.It Ic undivert
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Flushes the named output queues (or all queues if no arguments).
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.It Ic unix
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A pre-defined macro for testing the OS platform.
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.It Ic __line__
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Returns the current file's line number.
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.It Ic __file__
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Returns the current file's name.
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.El
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.Sh DIAGNOSTICS
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.Ex -std
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.Pp
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The
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.Ic m4exit
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macro may be used to change the exit status from the input file.
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.Sh COMPATIBILITY
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.Nm
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follows the Single Unix 2 specification, along with a few extensions taken
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from GNU-m4.
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Flags
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.Fl I , d ,
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and
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.Fl t
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are non-standard.
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.Pp
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The output format of tracing and of
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.Ic dumpdef
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are not specified in any standard,
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are likely to change and should not be relied upon.
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The current format of tracing is closely modelled on GNU-m4,
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to allow
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.Nm autoconf
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to work.
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.Pp
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For portability, one should not use the macros
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.Ic builtin ,
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.Ic esycmd ,
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.Ic expr ,
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.Ic indir ,
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.Ic paste ,
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.Ic patsubst ,
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.Ic regexp ,
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.Ic spaste ,
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.Ic unix ,
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.Ic __line__ ,
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and
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.Ic __file__ .
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.Pp
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All built-ins do expand without arguments in many other
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.Nm
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implementations.
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.Pp
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Many other
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.Nm
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implementations have dire size limitations with respect to buffer sizes.
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.Sh STANDARDS
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The
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.Nm
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utility
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conforms to
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.St -p1003.1-2001 .
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.Sh HISTORY
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An
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.Nm
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command appeared in PWB UNIX.
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.Sh AUTHORS
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.An -nosplit
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.An Ozan Yigit Aq oz@sis.yorku.ca
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and
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.An Richard A. O'Keefe Aq ok@goanna.cs.rmit.OZ.AU .
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GNU-m4 compatibility extensions by
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.An Marc Espie Aq espie@cvs.openbsd.org .
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