Tcl Built-In Commands regsub(1T)
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NAME
regsub - Perform substitutions based on regular expression
pattern matching
SYNOPSIS
regsub ?switches? exp string subSpec ?varName? |
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DESCRIPTION
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 ``&'' or ``\0'' or ``\n''
or backslash. The use of backslashes in subSpec tends to
interact badly with the Tcl parser's use of backslashes, so
it's 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 match-
ing range is found and substituted. If -all is
specified, then ``&'' and ``\n'' sequences are
handled for each substitution using the informa-
tion from the corresponding match.
-expanded Enables use of the expanded regular expres-
sion 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
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Tcl Built-In Commands regsub(1T)
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 `$' matches an empty string
before any newline in addition to its normal
function. This flag is equivalent to speci-
fying both -linestop and -lineanchor, or the
(?n) embedded option (see the re_syntax
manual page).
-linestop Changes the behavior of `[^' bracket expres-
sions and `.' so that they stop at newlines.
This is the same as specifying the (?p)
embedded option (see the re_syntax manual
page).
-lineanchor Changes the behavior of `^' and `$' (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; how-
ever, 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. When
using this switch, `^' will not match the begin-
ning of the line, and \A will still match the
start of the string at index. index will be con-
strained 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, oth- |
erwise the string after replacement is returned. See the
manual entry for regexp for details on the interpretation of
regular expressions.
EXAMPLES
Replace (in the string in variable string) every instance of
foo which is a word by itself with bar:
regsub -all {\} $string bar string
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Tcl Built-In Commands regsub(1T)
Insert double-quotes around the first instance of the word
interesting, however it is capitalised.
regsub -nocase {\} $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\u0100-\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]]
SEE ALSO
regexp(1T), re_syntax(1T), subst(1T)
KEYWORDS
match, pattern, regular expression, substitute
ATTRIBUTES
See attributes(5) for descriptions of the following attri-
butes:
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| ATTRIBUTE TYPE | ATTRIBUTE VALUE|
|____________________|__________________|_
| Availability | runtime/tcl-8 |
|____________________|__________________|_
| Interface Stability| Uncommitted |
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NOTES
Source for Tcl is available on http://opensolaris.org.
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