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Ruby Search and Replace
  • Last Updated : 25 Sep, 2019

sub and gsub string methods that use regular expressions, and their in-place variants are sub! and gsub!. The sub & sub! replaces the first occurrence of the pattern and gsub & gsub! replaces all occurrences. All of these methods perform a search-and-replace operation using a Regexp pattern. sub! and gsub! modify the string on which they are called whereas the sub and gsub returns a new string, leaving the original unmodified.
Below is the example to understand it better.

Example :

# Ruby program of sub and gsub method in a string
roll = "2004-959-559 # This is Roll Number"
# Delete Ruby-style comments
roll = roll.sub!(/#.*$/, "")   
puts "Roll Num : #{roll}"
# Remove anything other than digits
roll = roll.gsub!(/\D/, "")    
puts "Roll Num : #{roll}"

Output :

Roll Num : 2004-959-559 
Roll Num : 2004959559

In above example, we are using sub! and gsub!. here sub! replace first occurrence of the pattern and gsub! replaces all occurrences.

Example :

# Ruby program of sub and gsub method
text = "geeks for geeks, is a computer science portal"
# Change "rails" to "Rails" throughout
text.gsub!("geeks", "Geeks")
# Capitalize the word "Rails" throughout
text.gsub!(/\bgeeks\b/, "Geeks")
puts "#{text}"

Output :

Geeks for Geeks, is a computer science portal

The gsub! method too can be used with a regular expression.

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