Regular expressions (regex) look intimidating at first — a wall of symbols like ^[a-zA-Z0-9]+@[a-zA-Z0-9]+\.[a-z]+$ — but once you understand a handful of core symbols, you can read and write most common patterns.
What Regex Is Used For
Regex is a way to describe a pattern of text so you can search for it, validate it, or replace it. It's used in form validation (checking if an email looks valid), search-and-replace in text editors, data extraction, and filtering log files — anywhere you need to match text based on a pattern rather than an exact string.
Core Symbols to Know
| Symbol | Meaning |
|---|---|
. | Matches any single character |
* | Matches the previous character 0 or more times |
+ | Matches the previous character 1 or more times |
? | Makes the previous character optional |
\d | Matches any digit (0-9) |
\w | Matches any letter, digit, or underscore |
^ | Matches the start of a string |
$ | Matches the end of a string |
[abc] | Matches any one of the characters inside the brackets |
A Simple Example
The pattern \d{3}-\d{4} matches a phone-number-like format: three digits, a dash, then four digits (like "555-1234"). The {3} means "exactly 3 of the previous item" — in this case, three digits.
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