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 the start of each line in string
$ means the end of each line in string
() groups specific pattern
(?:) means this pattern will match in string BUT will not return it. E.g., 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, e.g. [abc] will match a or b or c. Ranges are supported too [a-c] will match the 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, e.g., İf you want to find . (which is a special character) in your string, you need to do this .
By combining these, you can create highly complicated pattern match/extraction functions with Regex.
Examples
^[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 the start of the string to the end of each line
^[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.
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