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Ruby Programming
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class Regexp
Parent: Object
Version: 1.6


compile escape last_match new quote == === =~ ~ casefold? kcode match source

A Regexp holds a regular expression, used to match a pattern against strings. Regexps are created using the /.../ and %r{...} literals, and by the constructor.


EXTENDED Ignore spaces and newlines in regexp.
IGNORECASE Matches are case insensitive.
MULTILINE Newlines treated as any other character.

class methods
compile Regexp.compile( pattern [, options [ lang ] ] ) -> aRegexp

Synonym for

escape Regexp.escape( aString ) -> aNewString

Escapes any characters that would have special meaning in a regular expression. For any string, Regexp.escape(str)=~str will be true.

Regexp.escape('\\*?{}.') \\\\\*\?\{\}\.

last_match Regexp.last_match -> aMatchData

Returns the MatchData object generated by the last successful pattern match. Equivalent to reading the global variable $~. MatchData is described on page 336.

new pattern [, options [ lang ] ] ) -> aRegexp

Constructs a new regular expression from pattern, which can be either a String or a Regexp (in which case that regexp's options are not propagated). If options is a Fixnum, it should be one or more of the constants Regexp::EXTENDED, Regexp::IGNORECASE, and Regexp::POSIXLINE, or-ed together. Otherwise, if options is not nil, the regexp will be case insensitive. The lang parameter enables multibyte support for the regexp: `n', `N' = none, `e', `E' = EUC, `s', `S' = SJIS, `u', `U' = UTF-8.

r1 ='^a-z+:\\s+\w+') /^a-z+:\s+\w+/
r2 =, true) /^a-z+:\s+\w+/i
r3 =, Regexp::EXTENDED) /^a-z+:\s+\w+/x

quote Regexp.quote( aString ) -> aNewString

Synonym for Regexp.escape.

instance methods
== rxp == aRegexp -> true or false

Equality---Two regexps are equal if their patterns are identical, they have the same character set code, and their casefold? values are the same.

/abc/  == /abc/x false
/abc/  == /abc/i false
/abc/u == /abc/n false

=== rxp === aString -> true or false

Case Equality---Synonym for Regexp#=~ used in case statements.

a = "HELLO"
case a
when /^a-z*$/; print "Lower case\n"
when /^A-Z*$/; print "Upper case\n"
else;            print "Mixed case\n"
Upper case

=~ rxp =~ aString -> anInteger or nil

Match---Matches rxp against aString, returning the offset of the start of the match or nil if the match failed.

/SIT/  =~ "insensitive" nil
/SIT/i =~ "insensitive" 5

~ ~ rxp -> anInteger or nil

Match---Matches rxp against the contents of $_. Equivalent to rxp =~ $_.

$_ = "input data"
~ /at/ 7

casefold? rxp.casefold? -> true or false

Returns the value of the case-insensitive flag.

kcode rxp.kcode -> aString

Returns the character set code for the regexp.

match rxp.match(aString) -> aMatchData or nil

Returns a MatchData object (see page 336) describing the match, or nil if there was no match. This is equivalent to retrieving the value of the special variable $~ following a normal match.

/(.)(.)(.)/.match("abc")[2] "b"

source rxp.source -> aString

Returns the original string of the pattern.

/ab+c/ix.source "ab+c"

Ruby Programming
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