- NAME
- regsub — Perform substitutions based on regular expression pattern matching
- SYNOPSIS
- DESCRIPTION
- -all
- -expanded
- -line
- -linestop
- -lineanchor
- -nocase
- -start index
- --
- EXAMPLES
- SEE ALSO
- KEYWORDS
regsub — Perform substitutions based on regular expression pattern matching
regsub ?switches? exp string subSpec ?varName?
This command matches the regular expression exp against
string,
and either copies string to the variable whose name is
given by varName or returns string if varName is not
present.
(Regular expression matching is described in the re_syntax
reference page.)
If there is a match, then while copying string to varName
(or to the result of this command if varName is not present)
the portion of string that
matched exp is replaced with subSpec.
If subSpec contains a
“&”
or
“\0”,
then it is replaced in the substitution with the portion of
string that matched exp.
If subSpec contains a
“\n”,
where n is a digit
between 1 and 9, then it is replaced in the substitution with
the portion of string that matched the n'th
parenthesized subexpression of exp.
Additional backslashes may be used in subSpec to prevent special
interpretation of
“&”,
“\0”,
“\n”
and backslashes.
The use of backslashes in subSpec tends to interact badly
with the Tcl parser's use of backslashes, so it is generally
safest to enclose subSpec in braces if it includes
backslashes.
If the initial arguments to regsub start with - then
they are treated as switches. The following switches are
currently supported:
- -all
-
All ranges in string that match exp are found and
substitution is performed for each of these ranges.
Without this switch only the first
matching range is found and substituted.
If -all is specified, then
“&”
and
“\n”
sequences are handled for each substitution using the information
from the corresponding match.
- -expanded
-
Enables use of the expanded regular expression syntax where
whitespace and comments are ignored. This is the same as specifying
the (?x) embedded option (see the re_syntax manual page).
- -line
-
Enables newline-sensitive matching. By default, newline is a
completely ordinary character with no special meaning. With this flag,
“[^”
bracket expressions and
“.”
never match newline,
“^”
matches an empty string after any newline in addition to its normal
function, and
“$”
matches an empty string before any newline in
addition to its normal function. This flag is equivalent to
specifying both -linestop and -lineanchor, or the
(?n) embedded option (see the re_syntax manual page).
- -linestop
-
Changes the behavior of
“[^”
bracket expressions and
“.”
so that they
stop at newlines. This is the same as specifying the (?p)
embedded option (see the re_syntax manual page).
- -lineanchor
-
Changes the behavior of
“^”
and
“$”
(the
“anchors”)
so they match the
beginning and end of a line respectively. This is the same as
specifying the (?w) embedded option (see the re_syntax
manual page).
- -nocase
-
Upper-case characters in string will be converted to lower-case
before matching against exp; however, substitutions specified
by subSpec use the original unconverted form of string.
- -start index
-
Specifies a character index offset into the string to start
matching the regular expression at.
The index value is interpreted in the same manner
as the index argument to string index.
When using this switch,
“^”
will not match the beginning of the line, and \A will still
match the start of the string at index.
index will be constrained to the bounds of the input string.
- --
-
Marks the end of switches. The argument following this one will
be treated as exp even if it starts with a -.
If varName is supplied, the command returns a count of the
number of matching ranges that were found and replaced, otherwise the
string after replacement is returned.
See the manual entry for regexp for details on the interpretation
of regular expressions.
Replace (in the string in variable string) every instance of
foo which is a word by itself with bar:
regsub -all {\mfoo\M} $string bar string
or (using the
“basic regular expression”
syntax):
regsub -all {(?b)\<foo\>} $string bar string
Insert double-quotes around the first instance of the word
interesting, however it is capitalized.
regsub -nocase {\yinteresting\y} $string {"&"} string
Convert all non-ASCII and Tcl-significant characters into \u escape
sequences by using regsub and subst in combination:
# This RE is just a character class for almost everything "bad"
set RE {[][{};#\\\$ \r\t\u0080-\uffff]}
# We will substitute with a fragment of Tcl script in brackets
set substitution {[format \\\\u%04x [scan "\\&" %c]]}
# Now we apply the substitution to get a subst-string that
# will perform the computational parts of the conversion. Note
# that newline is handled specially through string map since
# backslash-newline is a special sequence.
set quoted [subst [string map {\n {\\u000a}} \
[regsub -all $RE $string $substitution]]]
regexp, re_syntax, subst, string
match, pattern, quoting, regular expression, substitution
Copyright © 1993 The Regents of the University of California.
Copyright © 1994-1996 Sun Microsystems, Inc.
Copyright © 2000 Scriptics Corporation.