Metasploit Revealed: Secrets of the Expert Pentester

Regular expressions

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 ...