Common Ruby Regex Patterns

My earlier (rather lame) post on Ruby Regex’s (Regular Expressions) is getting some Google love, so I thought I would supplement it with some more useful information.

If you are searching for Ruby Regex help, my guess is you are looking for…

Validating an email address with a Ruby Regex

Something simple like this next one will get you started.

irb(main):023:0> “me@adamloving.com”.match /^([^@s]+)@((?:[-a-z0-9]+.)+[a-z]{2,})$/i

For a much more complete email address ruby regex, try:

#
# RFC822 Email Address Regex
# --------------------------
#
# Originally written by Cal Henderson
# c.f. http://iamcal.com/publish/articles/php/parsing_email/
#
# Translated to Ruby by Tim Fletcher, with changes suggested by Dan Kubb.
#
# Licensed under a Creative Commons Attribution-ShareAlike 2.5 License
# http://creativecommons.org/licenses/by-sa/2.5/
#
module RFC822
  EmailAddress = begin
    qtext = '[^\x0d\x22\x5c\x80-\xff]'
    dtext = '[^\x0d\x5b-\x5d\x80-\xff]'
    atom = '[^\x00-\x20\x22\x28\x29\x2c\x2e\x3a-' +
      '\x3c\x3e\x40\x5b-\x5d\x7f-\xff]+'
    quoted_pair = '\x5c[\x00-\x7f]'
    domain_literal = "\x5b(?:#{dtext}|#{quoted_pair})*\x5d"
    quoted_string = "\x22(?:#{qtext}|#{quoted_pair})*\x22"
    domain_ref = atom
    sub_domain = "(?:#{domain_ref}|#{domain_literal})"
    word = "(?:#{atom}|#{quoted_string})"
    domain = "#{sub_domain}(?:\x2e#{sub_domain})*"
    local_part = "#{word}(?:\x2e#{word})*"
    addr_spec = "#{local_part}\x40#{domain}"
    pattern = /A#{addr_spec}z/
  end
end

Find URLs using a Regular Expression in Ruby

Here is a simple URL matching regular expression.

irb(main):028:0> "http://www.adamloving.com/".match /^(http|https)://[a-z0-9]+([-.]{1}[a-z0-9]+)*.[a-z]{2,5}(([0-9]{1,5})?/.*)?$/ix

Ruby boolean operator (or ruby parsing) bug

This has bitten me a couple times in the last few days. The Ruby “or” (or equals) operator appears to have a bug where, when used in an assignment, the first value is assigned rather than the results of the entire expression.

irb(main):001:0> x = false || true
=> true
irb(main):002:0> x
=> true
irb(main):003:0> z = false or true
=> true
irb(main):004:0> z
=> false

ruby version: ruby 1.8.6 (2007-03-13 patchlevel 0) [i686-darwin8.10.1]

I would expect z to be true in that last example.

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