Remove obsolete include.
This commit is contained in:
Christopher Faylor
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.\" Copyright (c) 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)regexp.3 8.1 (Berkeley) 6/4/93
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.\"
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.Dd June 4, 1993
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.Dt REGEXP 3
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.Os
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.Sh NAME
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.Nm regcomp ,
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.Nm regexec ,
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.Nm regsub ,
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.Nm regerror
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.Nd regular expression handlers
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.Sh SYNOPSIS
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.Fd #include <regexp.h>
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.Ft regexp *
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.Fn regcomp "const char *exp"
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.Ft int
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.Fn regexec "const regexp *prog" "const char *string"
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.Ft void
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.Fn regsub "const regexp *prog" "const char *source" "char *dest"
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.Sh DESCRIPTION
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.Bf -symbolic
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This interface is made obsolete by
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.Xr regex 3 .
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It is available from the compatibility library, libcompat.
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.Ef
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.Pp
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The
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.Fn regcomp ,
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.Fn regexec ,
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.Fn regsub ,
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and
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.Fn regerror
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functions
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implement
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.Xr egrep 1 Ns -style
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regular expressions and supporting facilities.
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.Pp
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The
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.Fn regcomp
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function
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compiles a regular expression into a structure of type
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.Xr regexp ,
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and returns a pointer to it.
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The space has been allocated using
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.Xr malloc 3
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and may be released by
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.Xr free .
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.Pp
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The
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.Fn regexec
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function
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matches a
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.Dv NUL Ns -terminated
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.Fa string
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against the compiled regular expression
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in
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.Fa prog .
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It returns 1 for success and 0 for failure, and adjusts the contents of
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.Fa prog Ns 's
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.Em startp
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and
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.Em endp
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(see below) accordingly.
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.Pp
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The members of a
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.Xr regexp
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structure include at least the following (not necessarily in order):
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.Bd -literal -offset indent
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char *startp[NSUBEXP];
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char *endp[NSUBEXP];
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.Ed
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.Pp
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where
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.Dv NSUBEXP
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is defined (as 10) in the header file.
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Once a successful
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.Fn regexec
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has been done using the
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.Fn regexp ,
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each
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.Em startp Ns - Em endp
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pair describes one substring
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within the
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.Fa string ,
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with the
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.Em startp
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pointing to the first character of the substring and
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the
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.Em endp
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pointing to the first character following the substring.
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The 0th substring is the substring of
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.Fa string
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that matched the whole
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regular expression.
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The others are those substrings that matched parenthesized expressions
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within the regular expression, with parenthesized expressions numbered
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in left-to-right order of their opening parentheses.
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.Pp
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The
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.Fn regsub
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function
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copies
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.Fa source
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to
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.Fa dest ,
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making substitutions according to the
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most recent
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.Fn regexec
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performed using
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.Fa prog .
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Each instance of `&' in
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.Fa source
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is replaced by the substring
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indicated by
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.Em startp Ns Bq
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and
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.Em endp Ns Bq .
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Each instance of
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.Sq \e Ns Em n ,
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where
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.Em n
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is a digit, is replaced by
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the substring indicated by
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.Em startp Ns Bq Em n
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and
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.Em endp Ns Bq Em n .
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To get a literal `&' or
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.Sq \e Ns Em n
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into
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.Fa dest ,
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prefix it with `\e';
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to get a literal `\e' preceding `&' or
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.Sq \e Ns Em n ,
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prefix it with
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another `\e'.
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.Pp
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The
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.Fn regerror
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function
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is called whenever an error is detected in
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.Fn regcomp ,
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.Fn regexec ,
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or
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.Fn regsub .
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The default
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.Fn regerror
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writes the string
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.Fa msg ,
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with a suitable indicator of origin,
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on the standard
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error output
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and invokes
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.Xr exit 2 .
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The
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.Fn regerror
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function
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can be replaced by the user if other actions are desirable.
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.Sh REGULAR EXPRESSION SYNTAX
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A regular expression is zero or more
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.Em branches ,
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separated by `|'.
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It matches anything that matches one of the branches.
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.Pp
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A branch is zero or more
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.Em pieces ,
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concatenated.
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It matches a match for the first, followed by a match for the second, etc.
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.Pp
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A piece is an
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.Em atom
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possibly followed by `*', `+', or `?'.
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An atom followed by `*' matches a sequence of 0 or more matches of the atom.
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An atom followed by `+' matches a sequence of 1 or more matches of the atom.
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An atom followed by `?' matches a match of the atom, or the null string.
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.Pp
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An atom is a regular expression in parentheses (matching a match for the
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regular expression), a
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.Em range
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(see below), `.'
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(matching any single character), `^' (matching the null string at the
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beginning of the input string), `$' (matching the null string at the
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end of the input string), a `\e' followed by a single character (matching
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that character), or a single character with no other significance
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(matching that character).
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.Pp
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A
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.Em range
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is a sequence of characters enclosed in `[]'.
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It normally matches any single character from the sequence.
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If the sequence begins with `^',
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it matches any single character
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.Em not
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from the rest of the sequence.
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If two characters in the sequence are separated by `\-', this is shorthand
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for the full list of
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.Tn ASCII
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characters between them
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(e.g. `[0-9]' matches any decimal digit).
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To include a literal `]' in the sequence, make it the first character
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(following a possible `^').
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To include a literal `\-', make it the first or last character.
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.Sh AMBIGUITY
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If a regular expression could match two different parts of the input string,
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it will match the one which begins earliest.
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If both begin in the same place but match different lengths, or match
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the same length in different ways, life gets messier, as follows.
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.Pp
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In general, the possibilities in a list of branches are considered in
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left-to-right order, the possibilities for `*', `+', and `?' are
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considered longest-first, nested constructs are considered from the
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outermost in, and concatenated constructs are considered leftmost-first.
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The match that will be chosen is the one that uses the earliest
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possibility in the first choice that has to be made.
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If there is more than one choice, the next will be made in the same manner
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(earliest possibility) subject to the decision on the first choice.
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And so forth.
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.Pp
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For example,
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.Sq Li (ab|a)b*c
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could match
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`abc' in one of two ways.
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The first choice is between `ab' and `a'; since `ab' is earlier, and does
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lead to a successful overall match, it is chosen.
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Since the `b' is already spoken for,
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the `b*' must match its last possibility\(emthe empty string\(emsince
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it must respect the earlier choice.
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.Pp
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In the particular case where no `|'s are present and there is only one
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`*', `+', or `?', the net effect is that the longest possible
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match will be chosen.
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So
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.Sq Li ab* ,
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presented with `xabbbby', will match `abbbb'.
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Note that if
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.Sq Li ab* ,
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is tried against `xabyabbbz', it
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will match `ab' just after `x', due to the begins-earliest rule.
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(In effect, the decision on where to start the match is the first choice
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to be made, hence subsequent choices must respect it even if this leads them
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to less-preferred alternatives.)
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.Sh RETURN VALUES
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The
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.Fn regcomp
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function
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returns
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.Dv NULL
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for a failure
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.Pf ( Fn regerror
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permitting),
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where failures are syntax errors, exceeding implementation limits,
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or applying `+' or `*' to a possibly-null operand.
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.Sh SEE ALSO
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.Xr ed 1 ,
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.Xr ex 1 ,
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.Xr expr 1 ,
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.Xr egrep 1 ,
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.Xr fgrep 1 ,
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.Xr grep 1 ,
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.Xr regex 3
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.Sh HISTORY
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Both code and manual page for
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.Fn regcomp ,
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.Fn regexec ,
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.Fn regsub ,
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and
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.Fn regerror
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were written at the University of Toronto
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and appeared in
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.Bx 4.3 tahoe .
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They are intended to be compatible with the Bell V8
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.Xr regexp 3 ,
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but are not derived from Bell code.
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.Sh BUGS
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Empty branches and empty regular expressions are not portable to V8.
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.Pp
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The restriction against
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applying `*' or `+' to a possibly-null operand is an artifact of the
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simplistic implementation.
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.Pp
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Does not support
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.Xr egrep Ns 's
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newline-separated branches;
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neither does the V8
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.Xr regexp 3 ,
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though.
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.Pp
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Due to emphasis on
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compactness and simplicity,
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it's not strikingly fast.
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It does give special attention to handling simple cases quickly.
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