RegExp regexp, memos

April 22, 2013

Syntax
Usage
Links references

Syntax

Regexp

`[abc]`	A single character of: a, b or c
`[^abc]`	Any single character except: a, b, or c
`[a-z]`	Any single character in the range a-z
`[a-zA-Z]`	Any single character in the range a-z or A-Z
`^`	Start of line
`$`	End of line
`\A`	Start of string
`\z`	End of string
`.`	Any single character
`\s`	Any whitespace character
`\S`	Any non-whitespace character
`\d`	Any digit
`\D`	Any non-digit
`\w`	Any word character (letter, number, underscore)
`\W`	Any non-word character
`\b`	Any word boundary
`(...)`	Capture everything enclosed
`(a\|b)`	a or b
`a?`	Zero or one of a
`a*`	Zero or more of a
`a+`	One or more of a
`a{3}`	Exactly 3 of a
`a{3,}`	3 or more of a
`a{3,6}`	Between 3 and 6 of a
`aeiou*`	Match “aeio” followed by any number of “u”
`[aeiou]*`	Match any number of vowels
`(aeiou)*`	Match any number of sequences of “aeiou”
`(dog\|cat)`	Match either “dog” or “cat”

Usage

$1, $2… are the result of capture by ( ).

    reg = %r=my reg exp=
    reg = /my regexp/

    "string to test" =~ reg

Quick ways and api

    s = " 12 5 "
    r = / ([0-9]+)/
    p s[/ ([0-9]+)/, 1]
    x = s.match(r)
    x.pre_match
    x.post_match
    x.captures # or x.to_a

Back references

    pattern = /aa(\d+)-\1/
    pattern =~ 'aa1234-1234' # => 0
    pattern =~ 'aa1234-1233' # => nil

Greedy

    s = "Here another string"
    greedy = /[a-z]* [a-z]*/
    non_greedy = /[a-z]*? [a-z]*?/
    p greedy.match(s)[0]     # => "ere another"
    p non_greedy.match(s)[0] # => "ere "

    r = /<.*>/    # Greedy repetition: matches "<ruby>perl>"
    r = /<.*?>/   # Nongreedy: matches "<ruby>" in "<ruby>perl>"

Options

    /i         case insensitive
    /m         multiline mode - '.' will match newline
    /x         extended mode - whitespace is ignored
    /o         only interpolate #{} blocks once
    /[neus]    encoding: none, EUC, UTF-8, SJIS, respectively

RegExp regexp, memos

Syntax

Usage

Links references