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ActiveTcl User Guide |
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- NAME
- regsub - Perform substitutions based on regular expression
pattern matching
- SYNOPSIS
- regsub ?switches? exp string subSpec
?varName?
- 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 everything "bad"
set RE {[][{};#\\\$\s\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.
set quoted [subst [regsub -all $RE $string $substitution]]
regexp, re_syntax, subst, string
match, pattern, quoting, regular expression, substitute
Copyright © 1995-1997 Roger E. Critchlow Jr.
Copyright © 1993 The Regents of the University of California.
Copyright © 1994-1996 Sun Microsystems, Inc. Copyright ©
2000 Scriptics Corporation.