This blog post is firstly published on my personal blogging site kanby.net

TL;DR

  • Most common regex patterns
  • Examples of regex patterns

Most Common Patterns

Important: a x b in this example a is preceeding by x and b is followed by x

  • ^ means start of each line in string
  • $ means end of each line in string
  • () groups spesific pattern
  • (?:) means this pattern will match in string BUT will not return it. Eg. A phone number regex pattern must include country code but does not have to extract that part even though it must match on string.
  • [] matches specified single character, eg. [abc] will macth a or b or c. Ranges are supported too [a-c] will match same.
  • [^] matches every character except specified ones
  • . matches any single character
  • * 0 or more of the preceding element
  • + 1 or more of the preceding element
  • ? 0 or 1 of the preceding element
  • {n} Exactly n occurrences of the preceding element.
  • {n,} n or more occurrences of the preceding element.
  • {n,m} Between n and m occurrences of the preceding element
  • \d any digit
  • \D any non-digit
  • \w any word character (alphanumeric + underscore)
  • \W any non-word character
  • \s Matches any whitespace character
  • \S Matches any non-whitespace character
  • \ escape character, eg. İf you want to find . (which is a special character) in your string, you need to do this \.

With combining these, you can create highly complicated pattern match/extraction functions with Regex.

Examples

  1. \^[a-z_]+\.com$\ will match .com domains

    • [a-z_] means characters from a to z and underscore
    • + means at least one of them
    • \. means period (.)
    • com is for just com
    • ^ and $ is for searching from start of strin to end of each line

  2. ^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+.[a-zA-Z]{2,}$ will match emails

  • ^ Asserts the start of the string.

  • [a-zA-Z0-9._%+-]+ Matches one or more characters that can be:

    • Letters (a-z, A-Z)
    • Digits (0-9)
    • Underscores (_)
    • Dots (.)
    • Percent signs (%)
    • Plus signs (+)
    • Hyphens (-)

  • @ Matches the "@" symbol, which is mandatory in all email addresses.

  • [a-zA-Z0-9.-]+ Matches one or more characters for the domain name, allowing:

    • Letters (a-z, A-Z)
    • Digits (0-9)
    • Hyphens (-)
    • Dots (.)

  • \. Matches a literal dot (.) separating the domain name from the top-level domain (TLD).

  • [a-zA-Z]{2,} Matches the top-level domain (TLD) consisting of at least two letters (e.g., .com, .org).

  • $ Asserts the end of the string.

If you have any questions, Here is my Instagram @emrekanbay.en