Regular Expressions

.match(pattern)

Return the first match object for pattern, or nil.

s =  "The password is 123x123".match("(?<=The password is )\\S+")

→ 123x123

.match_all(pattern)

Return a vector of all matches.

puts  "4 languages, 1 Frankie".match_all("\\d+")

→ [4, 1]

.matches?(pattern)

True if pattern matches anywhere.

puts "4 languages, 1 Frankie".matches("\\d+")

→ true

=~

Match operator. Returns the position of the first match, or nil.

puts "frankie123" =~ "\\d+" 

→ 7

.sub(pattern, replacement)

Replace the first regex match.

puts "Frank1e".sub("\\d", "i") 

→ Frankie

.gsub(pattern, replacement)

Replace all regex matches with a fixed string.

puts "Frank1e 1s great!".gsub("\\d", "i") 

→ Frankie is great!

.gsub(pattern) do |m| … end

Replace all matches — block receives each match and returns its replacement.

puts "Round 1 of 3 starts in 5 seconds".gsub("\\d+") do |m|
  n = m.to_i
  suffix = if n == 1 then "st" elsif n == 2 then "nd" elsif n == 3 then "rd" else "th" end
  m + suffix
end

→ Round 1st of 3rd starts in 5th seconds

sub(str, pattern, rep)

Replace first match.

puts sub("Frakie is good", "good", "great!")

→ Frankie is great!

gsub(str, pattern, rep)

Replace all.

puts gsub("Ruby is great, Ruby is slick!", "Ruby", "Frankie")

→ Frankie is great, Frankie is slick!

match(str, pattern)

First match.

s = match("Frankie 101 and Frankie 102", "\\d+")
puts s[0]

→ 101

match_all(str, pattern)

All matches.

s = match_all("Frankie 101 and Frankie 102", "\\d+")
puts s

→ [101, 102]

matches(str, pattern)

Boolean test.

puts matches("Frankie", "\\d+") 

→ false

---

Standalone functions

sub(str, pattern, rep)

Replace first match

puts sub("Fran123ie" , "\\d+", "k")

→ Frankie

gsub(str, pattern, rep)

Replace all

puts gsub("Frank123ie 1is ru3nn1ing" , "\\d+", "")

→ Frankie is running

match(str, pattern)

First match.

matched = match("The password is 123x123", "(?<=The password is )\\S+")
puts matched[0]

→ 123x123

match_all(str, pattern)

All matches

matched =  "4 languages, 1 Frankie".match_all("\\d+")
puts matched

→ [4, 1]

matches(str, pattern)

Boolean test

puts matches("4 languages, 1 Frankie", "\\d+")

→ true