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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12 regexp ?switches? exp string ?matchVar? ?subMatchVar subMatchVar ...?
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17 Determines whether the regular expression exp matches part or all of
18 string and returns 1 if it does, 0 if it does not, unless -inline is
19 specified (see below). (Regular expression matching is described in
20 the re_syntax reference page.)
21 If additional arguments are specified after string then they are
23 treated as the names of variables in which to return information about
24 which part(s) of string matched exp. MatchVar will be set to the range
25 of string that matched all of exp. The first subMatchVar will contain
26 the characters in string that matched the leftmost parenthesized subex‐
27 pression within exp, the next subMatchVar will contain the characters
28 that matched the next parenthesized subexpression to the right in exp,
29 and so on.
30 If the initial arguments to regexp start with - then they are treated
32 as switches. The following switches are currently supported:
33 -about Instead of attempting to match the regular expression,
35 returns a list containing information about the regular
36 expression. The first element of the list is a subex‐
37 pression count. The second element is a list of prop‐
38 erty names that describe various attributes of the regu‐
39 lar expression. This switch is primarily intended for
40 debugging purposes.
41 -expanded Enables use of the expanded regular expression syntax
43 where whitespace and comments are ignored. This is the
44 same as specifying the (?x) embedded option (see the
45 re_syntax manual page).
46 -indices Changes what is stored in the subMatchVars. Instead of
48 storing the matching characters from string, each vari‐
49 able will contain a list of two decimal strings giving
50 the indices in string of the first and last characters
51 in the matching range of characters.
52 -line Enables newline-sensitive matching. By default, newline
54 is a completely ordinary character with no special mean‐
55 ing. With this flag, “[^” bracket expressions and “.”
56 never match newline, “^” matches an empty string after
57 any newline in addition to its normal function, and “$”
58 matches an empty string before any newline in addition
59 to its normal function. This flag is equivalent to
60 specifying both -linestop and -lineanchor, or the (?n)
61 embedded option (see the re_syntax manual page).
62 -linestop Changes the behavior of “[^” bracket expressions and “.”
64 so that they stop at newlines. This is the same as
65 specifying the (?p) embedded option (see the re_syntax
66 manual page).
67 -lineanchor Changes the behavior of “^” and “$” (the “anchors”) so
69 they match the beginning and end of a line respectively.
70 This is the same as specifying the (?w) embedded option
71 (see the re_syntax manual page).
72 -nocase Causes upper-case characters in string to be treated as
74 lower case during the matching process.
75 -all Causes the regular expression to be matched as many
77 times as possible in the string, returning the total
78 number of matches found. If this is specified with
79 match variables, they will contain information for the
80 last match only.
81 -inline Causes the command to return, as a list, the data that
83 would otherwise be placed in match variables. When
84 using -inline, match variables may not be specified. If
85 used with -all, the list will be concatenated at each
86 iteration, such that a flat list is always returned.
87 For each match iteration, the command will append the
88 overall match data, plus one element for each subexpres‐
89 sion in the regular expression. Examples are:
90 regexp -inline -- {\w(\w)} " inlined "
91 → in n
92 regexp -all -inline -- {\w(\w)} " inlined "
93 → in n li i ne e
94 -start index Specifies a character index offset into the string to
96 start matching the regular expression at. The index │
97 value is interpreted in the same manner as the index │
98 argument to string index. When using this switch, “^”
99 will not match the beginning of the line, and \A will
100 still match the start of the string at index. If
101 -indices is specified, the indices will be indexed
102 starting from the absolute beginning of the input
103 string. index will be constrained to the bounds of the
104 input string.
105 -- Marks the end of switches. The argument following this
107 one will be treated as exp even if it starts with a -.
108 If there are more subMatchVars than parenthesized subexpressions within
110 exp, or if a particular subexpression in exp does not match the string
111 (e.g. because it was in a portion of the expression that was not
112 matched), then the corresponding subMatchVar will be set to “-1 -1” if
113 -indices has been specified or to an empty string otherwise.
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116 Find the first occurrence of a word starting with foo in a string that
117 is not actually an instance of foobar, and get the letters following it
118 up to the end of the word into a variable:
119 regexp {\mfoo(?!bar\M)(\w*)} $string -> restOfWord
120 Note that the whole matched substring has been placed in the variable
121 “->”, which is a name chosen to look nice given that we are not actu‐
122 ally interested in its contents.
123 Find the index of the word badger (in any case) within a string and
125 store that in the variable location:
126 regexp -indices {(?i)\mbadger\M} $string location
127 This could also be written as a basic regular expression (as opposed to
128 using the default syntax of advanced regular expressions) match by pre‐
129 fixing the expression with a suitable flag:
130 regexp -indices {(?ib)\<badger\>} $string location
131 This counts the number of octal digits in a string:
133 regexp -all {[0-7]} $string
134 This lists all words (consisting of all sequences of non-whitespace
136 characters) in a string, and is useful as a more powerful version of
137 the split command:
138 regexp -all -inline {\S+} $string
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141 re_syntax(n), regsub(n), string(n) │
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144 match, parsing, pattern, regular expression, splitting, string
145Tcl 8.3 regexp(n)