How to match all occurrences of a regex

Question

Is there a quick way to find every match of a regular expression in Ruby? I've looked through the Regex object in the Ruby STL and searched on Google to no avail.

Answer 1

Using scan should do the trick:

string.scan(/regex/)

Answer 2

To find all the matching strings, use String's scan method.

str = "A 54mpl3 string w1th 7 numb3rs scatter36 ar0und"
str.scan(/\d+/)
#=> ["54", "3", "1", "7", "3", "36", "0"]

If you want, MatchData, which is the type of the object returned by the Regexp match method, use:

str.to_enum(:scan, /\d+/).map { Regexp.last_match }
#=> [#<MatchData "54">, #<MatchData "3">, #<MatchData "1">, #<MatchData "7">, #<MatchData "3">, #<MatchData "36">, #<MatchData "0">]

The benefit of using MatchData is that you can use methods like offset:

match_datas = str.to_enum(:scan, /\d+/).map { Regexp.last_match }
match_datas[0].offset(0)
#=> [2, 4]
match_datas[1].offset(0)
#=> [7, 8]

See these questions if you'd like to know more:

• "How do I get the match data for all occurrences of a Ruby regular expression in a string?"
• "Ruby regular expression matching enumerator with named capture support"
• "How to find out the starting point for each match in ruby"

Reading about special variables $&, $', $1, $2 in Ruby will be helpful too.

Answer 3

if you have a regexp with groups:

str="A 54mpl3 string w1th 7 numbers scatter3r ar0und"
re=/(\d+)[m-t]/

you can use String's scan method to find matching groups:

str.scan re
#> [["54"], ["1"], ["3"]]

To find the matching pattern:

str.to_enum(:scan,re).map {$&}
#> ["54m", "1t", "3r"]

Answer 4

You can use string.scan(your_regex).flatten. If your regex contains groups, it will return in a single plain array.

string = "A 54mpl3 string w1th 7 numbers scatter3r ar0und"
your_regex = /(\d+)[m-t]/
string.scan(your_regex).flatten
=> ["54", "1", "3"]

Regex can be a named group as well.

string = 'group_photo.jpg'
regex = /\A(?<name>.*)\.(?<ext>.*)\z/
string.scan(regex).flatten

You can also use gsub, it's just one more way if you want MatchData.

str.gsub(/\d/).map{ Regexp.last_match }