regexp - Match a regular expression against a string
regexp ?
switches?
exp string ?
matchVar?
?
subMatchVar subMatchVar ...?
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 expression 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
subMatchVar
will contain the characters in
string that matched the leftmost
parenthesized subexpression 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 containing 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 matchVar and
subMatchVars. Instead of storing the matching characters from
string, each variable will contain a list of two decimal 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 “$” matches an empty
string before any newline in addition to its normal function. This flag is
equivalent to specifying both -linestop and -lineanchor, or
the (?n) embedded option (see the re_syntax manual
page).
- -linestop
- Changes the behavior of “[^” bracket
expressions and “.” so that they stop at newlines. This is
the same as specifying the (?p) embedded option (see the
re_syntax manual page).
- -lineanchor
- Changes the behavior of “^” and
“$” (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 specified 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 iteration, 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 particular 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.
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
re_syntax(3tcl),
regsub(3tcl),
string(3tcl)
match, parsing, pattern, regular expression, splitting, string