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regexp(n) Tcl Built-In Commands regexp(n)
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NAME
regexp - Match a regular expression against a string
SYNOPSIS
regexp ?switches? exp string ?matchVar? ?subMatchVar subMatchVar ...?
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DESCRIPTION
Determines whether the regular expression exp matches part or all of string and returns 1
if it does, 0 if it does not, unless -inline is specified (see below). (Regular expres-
sion matching is described in the re_syntax reference page.)
If additional arguments are specified after string then they are treated as the names of
variables in which to return information about which part(s) of string matched exp.
MatchVar will be set to the range of string that matched all of exp. The first subMatch-
Var will contain the characters in string that matched the leftmost parenthesized subex-
pression within exp, the next subMatchVar will contain the characters that matched the
next parenthesized subexpression to the right in exp, and so on.
If the initial arguments to regexp start with - then they are treated as switches. The
following switches are currently supported:
-about Instead of attempting to match the regular expression, returns a list con-
taining information about the regular expression. The first element of the
list is a subexpression count. The second element is a list of property
names that describe various attributes of the regular expression. This
switch is primarily intended for debugging purposes.
-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).
-indices Changes what is stored in the subMatchVars. Instead of storing the match-
ing characters from string, each variable will contain a list of two deci-
mal strings giving the indices in string of the first and last characters
in the matching range of characters.
-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 "$" matches an empty
string before any newline in addition to its normal function. This flag is
equivalent to specifying both -linestop and -lineanchor, or the (?n) embed-
ded option (see the re_syntax manual page).
-linestop Changes the behavior of "[^" bracket expressions and "." so that they stop
at newlines. This is the same as specifying the (?p) embedded option (see
the re_syntax manual page).
-lineanchor Changes the behavior of "^" and "$" (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 Causes upper-case characters in string to be treated as lower case during
the matching process.
-all Causes the regular expression to be matched as many times as possible in
the string, returning the total number of matches found. If this is speci-
fied with match variables, they will contain information for the last match
only.
-inline Causes the command to return, as a list, the data that would otherwise be
placed in match variables. When using -inline, match variables may not be
specified. If used with -all, the list will be concatenated at each itera-
tion, such that a flat list is always returned. For each match iteration,
the command will append the overall match data, plus one element for each
subexpression in the regular expression. Examples are:
regexp -inline -- {\w(\w)} " inlined "
-> in n
regexp -all -inline -- {\w(\w)} " inlined "
-> in n li i ne e
-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. If -indices is specified, the indices will be indexed
starting from the absolute beginning of the input string. 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 there are more subMatchVars than parenthesized subexpressions within exp, or if a par-
ticular subexpression in exp does not match the string (e.g. because it was in a portion
of the expression that was not matched), then the corresponding subMatchVar will be set to
"-1 -1" if -indices has been specified or to an empty string otherwise.
EXAMPLES
Find the first occurrence of a word starting with foo in a string that is not actually an
instance of foobar, and get the letters following it up to the end of the word into a
variable:
regexp {\mfoo(?!bar\M)(\w*)} $string -> restOfWord
Note that the whole matched substring has been placed in the variable "->", which is a
name chosen to look nice given that we are not actually interested in its contents.
Find the index of the word badger (in any case) within a string and store that in the
variable location:
regexp -indices {(?i)\mbadger\M} $string location
This could also be written as a basic regular expression (as opposed to using the default
syntax of advanced regular expressions) match by prefixing the expression with a suitable
flag:
regexp -indices {(?ib)\<badger\>} $string location
This counts the number of octal digits in a string:
regexp -all {[0-7]} $string
This lists all words (consisting of all sequences of non-whitespace characters) in a
string, and is useful as a more powerful version of the split command:
regexp -all -inline {\S+} $string
SEE ALSO
re_syntax(n), regsub(n), string(n) |
KEYWORDS
match, parsing, pattern, regular expression, splitting, string
Tcl 8.3 regexp(n)
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On Apache
Under GNU General Public License
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