V8/usr/man/man3/regexp.3

.TH REGEXP 3
.SH NAME
regcomp, regexec, regsub, regerror \- regular expression handler
.SH SYNOPSIS
.nf
.B #include <regexp.h>
.PP
.B regexp *regcomp(exp)
.B char *exp;
.PP
.B int regexec(prog, string)
.B struct regexp *prog;
.B char *string;
.PP
.B regsub(prog, source, dest)
.B struct regexp *prog;
.B char *source;
.B char *dest;
.PP
.B regerror(msg)
.B char *msg;
.fi
.SH DESCRIPTION
.I Regcomp
compiles an
.IR egrep (1)-style regular expression and returns
a pointer to an object with the following structure.
The object is allocated by
.IR malloc (2)
and may be released by
.I free.
.IP
.nf
.so /usr/include/regexp.h
.fi
.PP
.IR Startp [ n ]
points to the first character of the substring of
.I string
that matches the
.IR n th
parenthesized subexpression (the subexpression
introduced by the
.IR n th
left parenthesis).
.IR Endp [ n ]
points to the first character following that substring.
The character array
.I program
contains the compiled form of the regular expression.
.PP
.I Regexec 
matches a null-terminated
.I string
against the compiled regular expression in
.I prog.
If it matches,
.I regexec
returns a non-zero value and fills in the
.I startp
and
.I endp
fields to describe the match, in which `*', `+', and `?' matches
are extended as far as possible.
By convention,
.IR startp [ 0 ]
and
.IR endp [ 0 ]
refer to the substring that matches the
complete regular expression.
.LP
.I Regsub
places in
.I dest
a substitution instance of
.I source
in the context of the last
.I regexec
performed using
.I prog.
Each instance of 
.RI `\e n ',
where
.I n
is a digit, is replaced by the
string delimited by
.IR startp [ n ]
and
.IR endp [ n ].
Each instance of `&' is replaced by the string delimited by
.I startp [0]
and
.I endp [0].
The result is placed in the area pointed to by 
.I dest .
.LP
.I Regerror,
called whenever an error is detected in
.I regcomp,
.I regexec,
or
.I regsub,
writes the string
.I msg
on the standard error file and exits.
.I Regerror
can be replaced to perform
special error processing.
.SH DIAGNOSTICS
.I Regcomp
returns 0 for an illegal expression
or other failure.
.I Regexec
returns 0 if
.I string 
is not accepted.
.SH "SEE ALSO"
egrep(1), expr(1)