String#scan

str.scan(pattern) -> array

The scan method searches a string for all occurrences of a given pattern and returns an array containing each match. Unlike match which returns only the first match, scan finds every occurrence.

Syntax

string.scan(pattern)

When given a regex pattern, scan returns an array of all matching substrings. If the regex contains capturing groups, each element of the returned array is an array of the captured groups.

Parameters

Parameter	Type	Default	Description
pattern	Regexp or String	—	The pattern to search for. Can be a regular expression or a plain string.

Examples

Basic string matching

text = "the quick brown fox jumps over the lazy dog"

text.scan("the")
# => ["the", "the"]

Using regular expressions

text = "I have 3 apples and 5 oranges"

text.scan(/\d+/)
# => ["3", "5"]

text.scan(/[aeiou]/)
# => ["a", "e", "a", "o", "e", "a", "o", "u", "e"]

With capturing groups

When the pattern contains capturing groups, scan returns arrays of the captured groups:

text = "John:25, Jane:30, Bob:22"

text.scan(/(\w+):(\d+)/)
# => [["John", "25"], ["Jane", "30"], ["Bob", "22"]]

Extracting emails from text

content = "Contact us at support@example.com or sales@company.org for help"

content.scan(/[\w.-]+@[\w.-]+\.\w+/)
# => ["support@example.com", "sales@company.org"]

Finding all words of a certain length

sentence = "Ruby is a powerful and expressive programming language"

sentence.scan(/\b\w{4,}\b/)
# => ["Ruby", "powerful", "expressive", "programming", "language"]

Common Patterns

With block form

When given a block, scan yields each match and returns the original string:

"hello world".scan(/\w+/) { |word| puts word.upcase }
# HELLO
# WORLD
# => "hello world"

Building a word frequency counter

text = "the quick brown fox jumps over the lazy dog the fox is quick"

words = text.scan(/\b\w+\b/)
frequency = words.tally
# => {"the"=>2, "quick"=>2, "brown"=>1, "fox"=>2, "jumps"=>1, ...}

Parsing structured data

data = "ID:001,ID:002,ID:003"

ids = data.scan(/ID:(\d+)/).flatten
# => ["001", "002", "003"]

See Also

• String#index
• String#rindex
• String#include?