1regexp(n) Tcl Built-In Commands regexp(n)
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8 regexp - Match a regular expression against a string
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11 regexp ?switches? exp string ?matchVar? ?subMatchVar subMatchVar ...?
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15 Determines whether the regular expression exp matches part or all of
16 string and returns 1 if it does, 0 if it does not, unless -inline is
17 specified (see below). (Regular expression matching is described in
18 the re_syntax reference page.)
19 If additional arguments are specified after string then they are
21 treated as the names of variables in which to return information about
22 which part(s) of string matched exp. MatchVar will be set to the range
23 of string that matched all of exp. The first subMatchVar will contain
24 the characters in string that matched the leftmost parenthesized subex‐
25 pression within exp, the next subMatchVar will contain the characters
26 that matched the next parenthesized subexpression to the right in exp,
27 and so on.
28 If the initial arguments to regexp start with - then they are treated
30 as switches. The following switches are currently supported:
31 -about Instead of attempting to match the regular expression,
33 returns a list containing information about the regular
34 expression. The first element of the list is a subex‐
35 pression count. The second element is a list of prop‐
36 erty names that describe various attributes of the regu‐
37 lar expression. This switch is primarily intended for
38 debugging purposes.
39 -expanded Enables use of the expanded regular expression syntax
41 where whitespace and comments are ignored. This is the
42 same as specifying the (?x) embedded option (see the
43 re_syntax manual page).
44 -indices Changes what is stored in the matchVar and subMatchVars.
46 Instead of storing the matching characters from string,
47 each variable will contain a list of two decimal strings
48 giving the indices in string of the first and last char‐
49 acters in the matching range of characters.
50 -line Enables newline-sensitive matching. By default, newline
52 is a completely ordinary character with no special mean‐
53 ing. With this flag, “[^” bracket expressions and “.”
54 never match newline, “^” matches an empty string after
55 any newline in addition to its normal function, and “$”
56 matches an empty string before any newline in addition
57 to its normal function. This flag is equivalent to
58 specifying both -linestop and -lineanchor, or the (?n)
59 embedded option (see the re_syntax manual page).
60 -linestop Changes the behavior of “[^” bracket expressions and “.”
62 so that they stop at newlines. This is the same as
63 specifying the (?p) embedded option (see the re_syntax
64 manual page).
65 -lineanchor Changes the behavior of “^” and “$” (the “anchors”) so
67 they match the beginning and end of a line respectively.
68 This is the same as specifying the (?w) embedded option
69 (see the re_syntax manual page).
70 -nocase Causes upper-case characters in string to be treated as
72 lower case during the matching process.
73 -all Causes the regular expression to be matched as many
75 times as possible in the string, returning the total
76 number of matches found. If this is specified with
77 match variables, they will contain information for the
78 last match only.
79 -inline Causes the command to return, as a list, the data that
81 would otherwise be placed in match variables. When
82 using -inline, match variables may not be specified. If
83 used with -all, the list will be concatenated at each
84 iteration, such that a flat list is always returned.
85 For each match iteration, the command will append the
86 overall match data, plus one element for each subexpres‐
87 sion in the regular expression. Examples are:
88 regexp -inline -- {\w(\w)} " inlined "
90 → in n
91 regexp -all -inline -- {\w(\w)} " inlined "
92 → in n li i ne e
93 -start index Specifies a character index offset into the string to
95 start matching the regular expression at. The index
96 value is interpreted in the same manner as the index
97 argument to string index. When using this switch, “^”
98 will not match the beginning of the line, and \A will
99 still match the start of the string at index. If
100 -indices is specified, the indices will be indexed
101 starting from the absolute beginning of the input
102 string. index will be constrained to the bounds of the
103 input string.
104 -- Marks the end of switches. The argument following this
106 one will be treated as exp even if it starts with a -.
107 If there are more subMatchVars than parenthesized subexpressions within
109 exp, or if a particular subexpression in exp does not match the string
110 (e.g. because it was in a portion of the expression that was not
111 matched), then the corresponding subMatchVar will be set to “-1 -1” if
112 -indices has been specified or to an empty string otherwise.
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115 Find the first occurrence of a word starting with foo in a string that
116 is not actually an instance of foobar, and get the letters following it
117 up to the end of the word into a variable:
118 regexp {\mfoo(?!bar\M)(\w*)} $string -> restOfWord
120 Note that the whole matched substring has been placed in the variable
122 “->”, which is a name chosen to look nice given that we are not actu‐
123 ally interested in its contents.
124 Find the index of the word badger (in any case) within a string and
126 store that in the variable location:
127 regexp -indices {(?i)\mbadger\M} $string location
129 This could also be written as a basic regular expression (as opposed to
131 using the default syntax of advanced regular expressions) match by pre‐
132 fixing the expression with a suitable flag:
133 regexp -indices {(?ib)\<badger\>} $string location
135 This counts the number of octal digits in a string:
137 regexp -all {[0-7]} $string
139 This lists all words (consisting of all sequences of non-whitespace
141 characters) in a string, and is useful as a more powerful version of
142 the split command:
143 regexp -all -inline {\S+} $string
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147 re_syntax(n), regsub(n), string(n)
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150 match, parsing, pattern, regular expression, splitting, string
151Tcl 8.3 regexp(n)