'\"
'\" Copyright (c) 1993 The Regents of the University of California.
'\" Copyright (c) 1994-1996 Sun Microsystems, Inc.
'\"
'\" See the file "license.terms" for information on usage and redistribution
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
'\" 
'\" RCS: @(#) $Id: regsub.n,v 1.4 1999/09/21 04:20:36 hobbs Exp $
'\" 
.so man.macros
.TH regsub n 8.3 Tcl "Tcl Built-In Commands"
.BS
'\" Note:  do not modify the .SH NAME line immediately below!
.SH NAME
regsub \- Perform substitutions based on regular expression pattern matching
.SH SYNOPSIS
\fBregsub \fR?\fIswitches\fR? \fIexp string subSpec varName\fR
.BE

.SH DESCRIPTION
.PP
This command matches the regular expression \fIexp\fR against
\fIstring\fR,
and it copies \fIstring\fR to the variable whose name is
given by \fIvarName\fR.
(Regular expression matching is described in the \fBre_syntax\fR
reference page.)
If there is a match, then while copying \fIstring\fR to \fIvarName\fR
the portion of \fIstring\fR that
matched \fIexp\fR is replaced with \fIsubSpec\fR.
If \fIsubSpec\fR contains a ``&'' or ``\e0'', then it is replaced
in the substitution with the portion of \fIstring\fR that
matched \fIexp\fR.
If \fIsubSpec\fR contains a ``\e\fIn\fR'', where \fIn\fR is a digit
between 1 and 9, then it is replaced in the substitution with
the portion of \fIstring\fR that matched the \fIn\fR-th
parenthesized subexpression of \fIexp\fR.
Additional backslashes may be used in \fIsubSpec\fR to prevent special
interpretation of ``&'' or ``\e0'' or ``\e\fIn\fR'' or
backslash.
The use of backslashes in \fIsubSpec\fR tends to interact badly
with the Tcl parser's use of backslashes, so it's generally
safest to enclose \fIsubSpec\fR in braces if it includes
backslashes.
.LP
If the initial arguments to \fBregexp\fR start with \fB\-\fR then
they are treated as switches.  The following switches are
currently supported:
.TP 10
\fB\-all\fR
All ranges in \fIstring\fR that match \fIexp\fR are found and
substitution is performed for each of these ranges.
Without this switch only the first
matching range is found and substituted.
If \fB\-all\fR is specified, then ``&'' and ``\e\fIn\fR''
sequences are handled for each substitution using the information
from the corresponding match.
.TP 10
\fB\-nocase\fR
Upper-case characters in \fIstring\fR will be converted to lower-case
before matching against \fIexp\fR;  however, substitutions specified
by \fIsubSpec\fR use the original unconverted form of \fIstring\fR.
.VS 8.3
.TP 10
\fB\-start\fR \fIindex\fR
Specifies a character index offset into the string to start
matching the regular expression at.  When using this switch, `^'
will not match the beginning of the line, and \\A will still
match the start of the string at \fIindex\fR.  If \fB\-indices\fR
is specified, the indices will be indexed starting from the
absolute beginning of the input string.
\fIindex\fR will be constrained to the bounds of the input string.
.VE 8.3
.TP 10
\fB\-\|\-\fR
Marks the end of switches.  The argument following this one will
be treated as \fIexp\fR even if it starts with a \fB\-\fR.
.PP
The command returns a count of the number of matching ranges that
were found and replaced.
See the manual entry for \fBregexp\fR for details on the interpretation
of regular expressions.

.SH KEYWORDS
match, pattern, regular expression, substitute
