MEPX
Chapter 6 of 10All chapters
  1. 1What a regex is
  2. 2Literals and classes
  3. 3Quantifiers
  4. 4Anchors and boundaries
  5. 5Groups and alternation
  6. 6Escaping
  7. 7Lookaround
  8. 8Flags
  9. 9When regex goes wrong
  10. 10Writing readable patterns

Chapter 6 of 10

Escaping

Matching the special characters themselves.

The metacharacters

Roughly a dozen characters have meaning: . * + ? ^ $ | ( ) [ ] { } and the backslash itself. To match one literally, put a backslash before it.

  • A dot inside square brackets is already literal, so [.] needs no escape.
  • Most languages offer a function to escape a whole string for use in a pattern.

Double escaping

In most languages the pattern is first a string, so the backslash must survive the string literal too. That is why a digit class is written as \\d in source code and \d in a regex tester.