1regsub(n) Tcl Built-In Commands regsub(n)
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8 regsub - Perform substitutions based on regular expression pattern
9 matching
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12 regsub ?switches? exp string subSpec ?varName?
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16 This command matches the regular expression exp against string, and
17 either copies string to the variable whose name is given by varName or
18 returns string if varName is not present. (Regular expression matching
19 is described in the re_syntax reference page.) If there is a match,
20 then while copying string to varName (or to the result of this command
21 if varName is not present) the portion of string that matched exp is
22 replaced with subSpec. If subSpec contains a “&” or “\0”, then it is
23 replaced in the substitution with the portion of string that matched
24 exp. If subSpec contains a “\n”, where n is a digit between 1 and 9,
25 then it is replaced in the substitution with the portion of string that
26 matched the n'th parenthesized subexpression of exp. Additional back‐
27 slashes may be used in subSpec to prevent special interpretation of
28 “&”, “\0”, “\n” and backslashes. The use of backslashes in subSpec
29 tends to interact badly with the Tcl parser's use of backslashes, so it
30 is generally safest to enclose subSpec in braces if it includes back‐
31 slashes.
32 If the initial arguments to regsub start with - then they are treated
34 as switches. The following switches are currently supported:
35 -all All ranges in string that match exp are found and substitution
37 is performed for each of these ranges. Without this switch only
38 the first matching range is found and substituted. If -all is
39 specified, then “&” and “\n” sequences are handled for each sub‐
40 stitution using the information from the corresponding match.
41 -expanded
43 Enables use of the expanded regular expression syntax where
44 whitespace and comments are ignored. This is the same as speci‐
45 fying the (?x) embedded option (see the re_syntax manual page).
46 -line Enables newline-sensitive matching. By default, newline is a
48 completely ordinary character with no special meaning. With
49 this flag, “[^” bracket expressions and “.” never match new‐
50 line, “^” matches an empty string after any newline in addition
51 to its normal function, and “$” matches an empty string before
52 any newline in addition to its normal function. This flag is
53 equivalent to specifying both -linestop and -lineanchor, or the
54 (?n) embedded option (see the re_syntax manual page).
55 -linestop
57 Changes the behavior of “[^” bracket expressions and “.” so
58 that they stop at newlines. This is the same as specifying the
59 (?p) embedded option (see the re_syntax manual page).
60 -lineanchor
62 Changes the behavior of “^” and “$” (the “anchors”) so they
63 match the beginning and end of a line respectively. This is the
64 same as specifying the (?w) embedded option (see the re_syntax
65 manual page).
66 -nocase
68 Upper-case characters in string will be converted to lower-case
69 before matching against exp; however, substitutions specified
70 by subSpec use the original unconverted form of string.
71 -start index
73 Specifies a character index offset into the string to start
74 matching the regular expression at. The index value is inter‐
75 preted in the same manner as the index argument to string index.
76 When using this switch, “^” will not match the beginning of the
77 line, and \A will still match the start of the string at index.
78 index will be constrained to the bounds of the input string.
79 -- Marks the end of switches. The argument following this one will
81 be treated as exp even if it starts with a -.
82 If varName is supplied, the command returns a count of the number of
84 matching ranges that were found and replaced, otherwise the string
85 after replacement is returned. See the manual entry for regexp for
86 details on the interpretation of regular expressions.
87
89 Replace (in the string in variable string) every instance of foo which
90 is a word by itself with bar:
91 regsub -all {\mfoo\M} $string bar string
93 or (using the “basic regular expression” syntax):
95 regsub -all {(?b)\<foo\>} $string bar string
97 Insert double-quotes around the first instance of the word interesting,
99 however it is capitalized.
100 regsub -nocase {\yinteresting\y} $string {"&"} string
102 Convert all non-ASCII and Tcl-significant characters into \u escape
104 sequences by using regsub and subst in combination:
105 # This RE is just a character class for almost everything "bad"
107 set RE {[][{};#\\\$ \r\t\u0080-\uffff]}
108 # We will substitute with a fragment of Tcl script in brackets
110 set substitution {[format \\\\u%04x [scan "\\&" %c]]}
111 # Now we apply the substitution to get a subst-string that
113 # will perform the computational parts of the conversion. Note
114 # that newline is handled specially through string map since
115 # backslash-newline is a special sequence.
116 set quoted [subst [string map {\n {\\u000a}} \
117 [regsub -all $RE $string $substitution]]]
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120 regexp(n), re_syntax(n), subst(n), string(n)
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123 match, pattern, quoting, regular expression, substitution
124Tcl 8.3 regsub(n)