Regular Expressions

Regular Expressions

• Avoid using $1-9 as it can be hard to track
  what they contain. Named groups can be used instead.
  [link]

  # bad
  /(regexp)/ =~ string
  ...
  process $1

  # good
  /(?<meaningful_var>regexp)/ =~ string
  ...
  process meaningful_var

• Be careful with ^ and $ as they
  match start/end of line, not string endings. If you want to match the whole
  string use: \A and \z.[link]

  string = "some injection\nusername"
  string[/^username$/]   # matches
  string[/\Ausername\z/] # don't match

• Use x modifier for complex regexps. This makes
  them more readable and you can add some useful comments. Just be careful as
  spaces are ignored.[link]

  regexp = %r{
    start         # some text
    \s            # white space char
    (group)       # first group
    (?:alt1|alt2) # some alternation
    end
  }x