On the use of regular expressions in Ruby _ruby special topic

If you just need to find the text of the string, do not use regular expressions: string[' text '

For simple structures, you can query directly using the string[/re/] approach.

  Match = string[/regexp/]       # Get content of matched regexp
  first_group = string[/text (GRP)/, 1] # get content of Cap tured Group
  String[/text (GRP)/, 1] = ' Replace ' # string => ' text replace '

When you don't need to group results, use groups that are not grouped.

  /(First|second)/  # bad
  /(?: First|second)/# Good

Do not use Perl legacy variables to represent matching regular groupings (such as $1,$2, etc.), using regexp.last_match[n] as an alternative.

  /(RegExp)/=~ string
  ...

  # bad
  process

  # good
  process regexp.last_match[1]

It's hard to understand what they mean by avoiding the use of digital naming groups. Named groups to override.

  # Bad
  /(regexp)/=~ string
  ...
  Process regexp.last_match[1]

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

The character class has the following special keywords to note: ^,-, \,], so, do not escape. or parentheses in the [].

Note that ^ and $, they match the beginning and end of the line, not the ending of a string, if you want to match the entire string, with \a and \z.

  String = "Some Injection\nusername"
  string[/^username$/]  # matches
  string[/\ausername\z/] # don ' t Match

For complex regular expressions, use an x modifier. You can improve readability and add useful annotations. Just be aware that whitespace characters are ignored.

  RegExp =%r{
   start     # some text
   \s      # white space char
   (group)    # a
   (?: alt1| ALT2) # Some alternation
   end
  }x

Sub/gsub also supports hashing and code block formal syntax, which can be used in complex case substitution operations.