Regular Expressions (RegEx)

Introduction

Regular expressions (RegEx) are like blueprints for searching and manipulating text. They allow you to find, replace, and validate data with precision. At its core, a regular expression is a sequence of characters and symbols that forms a search pattern.
RegEx is integrated into many tools (like grep and sed) and programming languages.

Basic Syntax and Special Characters

. (dot): Matches any single character except a newline.
* (asterisk): Matches zero or more occurrences of the preceding character or pattern.
+ (plus): Matches one or more occurrences of the preceding character or pattern.
? (question mark): Matches zero or one occurrence of the preceding character or pattern.
^ (caret): Matches the beginning of a line.
$ (dollar sign): Matches the end of a line.
\d: Matches any digit (0-9).
\w: Matches any word character (letters, digits, or underscores).
\s: Matches any whitespace character (space, tab, or newline).
\b: Matches a word boundary (start or end of a word).

Grouping in RegEx

Grouping lets you combine multiple characters or patterns. There are three common types of brackets used:
- () (Parentheses): Capturing groups
  - Example: (abc)+ matches "abc", "abcabc", "abcabcabc".
- [] (Square brackets): Character classes
  - Example: [aeiou] matches any vowel.
- {} (Curly brackets): Quantifiers
  - Example: a{2,4} matches "aa", "aaa", or "aaaa".

Other Useful Operators in RegEx

OR (|): Matches either pattern on the left or right side of |.
- Example: cat|dog matches "cat" or "dog".
Negation ([^]): Matches any character except those inside brackets.
- Example: [^0-9] matches any non-digit character.
Escape Character (\): Used to escape special characters like . or *.
- Example: \. matches a literal period ..

Common Use Cases

Validate an email address:

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

Extract phone numbers:
```
\b\d{3}[-.]?\d{3}[-.]?\d{4}\b
```
Find words that start with a capital letter:
```
\b[A-Z][a-z]*\b
```

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Last updated 1 month ago

Introduction

Regular expressions (RegEx) are like blueprints for searching and manipulating text. They allow you to find, replace, and validate data with precision. At its core, a regular expression is a sequence of characters and symbols that forms a search pattern.

RegEx is integrated into many tools (like grep and sed) and programming languages.

Basic Syntax and Special Characters

. (dot): Matches any single character except a newline.

* (asterisk): Matches zero or more occurrences of the preceding character or pattern.

+ (plus): Matches one or more occurrences of the preceding character or pattern.

? (question mark): Matches zero or one occurrence of the preceding character or pattern.

^ (caret): Matches the beginning of a line.

$ (dollar sign): Matches the end of a line.

\d: Matches any digit (0-9).

\w: Matches any word character (letters, digits, or underscores).

\s: Matches any whitespace character (space, tab, or newline).

\b: Matches a word boundary (start or end of a word).

Grouping in RegEx

Grouping lets you combine multiple characters or patterns. There are three common types of brackets used:

() (Parentheses): Capturing groups
- Example: (abc)+ matches "abc", "abcabc", "abcabcabc".
[] (Square brackets): Character classes
- Example: [aeiou] matches any vowel.
{} (Curly brackets): Quantifiers
- Example: a{2,4} matches "aa", "aaa", or "aaaa".

Other Useful Operators in RegEx

OR (|): Matches either pattern on the left or right side of |.

Example: cat|dog matches "cat" or "dog".

Negation ([^]): Matches any character except those inside brackets.

Example: [^0-9] matches any non-digit character.

Escape Character (\): Used to escape special characters like . or *.

Example: \. matches a literal period ..