[ Try Hack Me ] Regular expressions

Task 1: Introduction

Task 2: Charsets

• Match all of the following characters: c, o, g

A: [cog]

• Match all of the following words: cat, fat, hat

A: [cfh]at

• Match all of the following words: Cat, cat, Hat, hat

A: [cChH]at

• Match all of the following filenames: File1, File2, file3, file4, file5, File7, file9

A: [fF]ile[1–9]

• Match all of the filenames of question 4, except “File7” (use the hat symbol)

A: [fF]ile[^7]

Task 3: Wildcards and optional characters

• Match all of the following words: Cat, fat, hat, rat

A: .at

• Match all of the following words: Cat, cats

A: [cC]ats?

• Match the following domain name: cat.xyz

A: cat\.xyz

• Match all of the following domain names: cat.xyz, cats.xyz, hats.xyz

A: [ch]ats?\.xyz

• Match every 4-letter string that doesn’t end in any letter from n to z

A: …[^n-z]

• Match bat, bats, hat, hats, but not rat or rats (use the hat symbol)

A: [^r]ats?

Task 4: Metacharacters and repetitions

• Match the following word: catssss
• Match all of the following words (use the * sign): Cat, cats, catsss
• Match all of the following sentences (use the + sign): regex go br, regex go brrrrrr
• Match all of the following filenames: ab0001, bb0000, abc1000, cba0110, c0000 (don’t use a metacharacter)
• Match all of the following filenames: File01, File2, file12, File20, File99
• Match all of the following folder names: kali tools, kali tools
• Match all of the following filenames: notes~, stuff@, gtfob#, lmaoo!
• Match the string in quotes (use the * sign and the \s, \S metacharacters): “2f0h@f0j0%! a)K!F49h!FFOK”
• Match every 9-character string (with letters, numbers, and symbols) that doesn’t end in a “!” sign
• Match all of these filenames (use the + symbol): .bash_rc, .unnecessarily_long_filename, and note1

Task 5: Starts with/ ends with, groups, and either/ or

• Match every string that starts with “Password:” followed by any 10 characters excluding “0”

A: Password:[^0]{10}

• Match “username: “ in the beginning of a line (note the space!)

A: ^username:\S

• Match every line that doesn’t start with a digit (use a metacharacter)

A: ^\D

• Match this string at the end of a line: EOF$

A: EOF\$$

• Match all of the following sentences:

I use nano

I use vim

A: I use (nano|vim)

• Match all lines that start with $, followed by any single digit,
  followed by $, followed by one or more non-whitespace characters

A: ^\$\d\$\S+

• Match every possible IPv4 IP address (use metacharacters and groups)

A: (\d{1,3}\.){3}\d{1,3}

• Match all of these emails while also adding the username and the domain name (not the TLD) in separate groups (use \w): hello@tryhackme.com, username@domain.com, dummy_email@xyz.com

A: (\w+)@(\w+)\.com

Task 6: Conclusion