regex
Regular expressions (regex) are powerful tools for searching and manipulating text. This cheat sheet provides a quick overview of common elements and examples:
Characters:
Literal Characters: Match them exactly (e.g.,
a,1,$).Wildcard (
*): Matches any character (except newline) zero or more times (e.g.,colou?rmatches "color" and "colour").Plus (
+): Matches any character one or more times (e.g.,\d+matches one or more digits).Question Mark (
?): Matches the preceding character zero or one time (e.g.,fa?mousmatches "famous" and "famus").Character Classes (
[]): Matches any single character within the brackets (e.g.,[aeiou]matches any vowel).Negation (
^inside[]): Matches any character NOT in the brackets (e.g.,[^aeiou]matches any consonant).Ranges (
-): Matches characters within a range (e.g.,[a-z]matches any lowercase letter).
Anchors:
Caret (
^): Matches the beginning of the string (e.g.,^hellomatches only "hello").Dollar Sign (
$): Matches the end of the string (e.g.,world$matches only "world").Word Boundary (
\b): Matches the beginning or end of a word (e.g.,\bcat\bmatches "cat" but not "category").
Quantifiers:
Curly Braces (
{n,m}): Matches the preceding character n to m times (e.g.,colou{2}matches "colour" but not "color").
Grouping:
Parentheses (
()): Groups characters together for operations (e.g.,(Mr|Ms)\.matches "Mr." or "Ms.").
Backreferences:
\followed by a number: Matches the content captured by the corresponding numbered group (e.g.,(\d{3})-(\d{3})-(\d{4}),$1-$2-$3extracts phone number parts).
Flags:
i: Case-insensitive matching (e.g.,Catmatches "CAT").m: Multiline mode (e.g.,^$matches empty lines).s: Dot matches any character, including newlines.
Examples:
Extract email addresses:
^a-zA-Z0-9.!#$%&'*+/=?^_{1,63}@[a-zA-Z0-9: ?:[a-zA-Z0-9-]{0,61}[a-zA-Z0-9]?.[a-zA-Z]{2,6}$`Validate US phone numbers:
^\(?([0-9]{3})\)?[-. ]?([0-9]{3})[-. ]?([0-9]{4})$Match all words starting with "cat":
\bcat\w*
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