Regular expressions basics

Anchors

^a - Maches anything that starts after a.
$b - Matches anything that ends with b.

Ranges

• Ranges are described in square brackets []
• Using ^ inside range bracets negates the character that follows.
  • Example: [^7] - Match everything except the number 7.
• [A-Z] - Matches characters that are one among A through Z.
  • Example: [A-Za-z]

Boundaries

• \s - Whitespace
  • Example: \sstark -> Matches tony stark.
• \b - Word boundary
  • Example:
    • \bstark -> Matches tony stark & tony-stark but not tonystark.
    • \brobinhood\b -> Matches robinhood but not robin or hood.
• Uppercase \s & \b negates its properties.

Quantifiers

• Quantifiers specify how many of the previous characters are allowed.
• b* -> Matches b 0 or more times.
• b? -> Matches b 0 or once only(optional)
• b+ -> Matches one or more occurence of b.
• b{3} -> Matches exactly 3 occurences.
  • Example: uuu

• . -> Match any single character.

• Use \ backslash to escape meta characters.

• ^$ - Matches empty lines.