Regular expressions are used to match a string or its number of occurrences in a given set of strings or a sentence. The concept of regular expressions is critical when it comes to Metasploit. We use regular expressions in most cases while writing fuzzers, scanners, analyzing the response from a given port, and so on.
Let's have a look at an example of a program that demonstrates the usage of regular expressions.
Consider a scenario where we have a variable, n, with the value Hello world, and we need to design regular expressions for it. Let's have a look at the following code snippet:
irb(main):001:0> n = "Hello world" => "Hello world" irb(main):004:0> r = /world/ => /world/ irb(main):005:0> r.match n => #<MatchData "world"> ...
