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.\"     @(#)re_comp.3	8.1 (Berkeley) 6/4/93
.\"
.Dd $Mdocdate: May 31 2007 $
.Dt RE_COMP 3
.Os
.Sh NAME
.Nm re_comp ,
.Nm re_exec
.Nd regular expression handler
.Sh SYNOPSIS
.Fd #include <unistd.h>
.Ft char *
.Fn re_comp "const char *s"
.Ft int
.Fn re_exec "const char *s"
.Sh DESCRIPTION
.Bf -symbolic
This interface is made obsolete by
.Xr regex 3 .
It is available from the compatibility library, libcompat.
.Ef
.Pp
The
.Fn re_comp
function
compiles a string into an internal form suitable for pattern matching.
The
.Fn re_exec
function
checks the argument string against the last string passed to
.Fn re_comp .
.Pp
The
.Fn re_comp
function
returns 0 if the string
.Fa s
was compiled successfully; otherwise a string containing an
error message is returned.
If
.Fn re_comp
is passed 0 or a null string, it returns without changing the currently
compiled regular expression.
.Pp
The
.Fn re_exec
function
returns 1 if the string
.Fa s
matches the last compiled regular expression, 0 if the string
.Fa s
failed to match the last compiled regular expression, and \-1 if the compiled
regular expression was invalid (indicating an internal error).
.Pp
The strings passed to both
.Fn re_comp
and
.Fn re_exec
may have trailing or embedded newline characters;
they are terminated by
.Dv NUL Ns s.
The regular expressions recognized are described in the manual entry for
.Xr ed 1 ,
given the above difference.
.Sh DIAGNOSTICS
The
.Fn re_exec
function
returns \-1 for an internal error.
.Pp
The
.Fn re_comp
function
returns one of the following strings if an error occurs:
.Bd -unfilled -offset indent
No previous regular expression,
Regular expression too long,
unmatched \e(,
missing ],
too many \e(\e) pairs,
unmatched \e).
.Ed
.Sh SEE ALSO
.Xr ed 1 ,
.Xr egrep 1 ,
.Xr ex 1 ,
.Xr fgrep 1 ,
.Xr grep 1 ,
.Xr regex 3
.Sh HISTORY
The
.Fn re_comp
and
.Fn re_exec
functions appeared in
.Bx 4.0 .