1. \d any Digit

  2. . any Character

  3. . Period

  4. [abc] Only a, b, or c

  5. [^abc] Not a, b, nor c

  6. [a-z] Characters a to z

  7. [0-9] Numbers 0 to 9

  8. {m} m Repetitions

  9. {m,n} m to n Repetitions

    eg. a{1,} means >=1 occurance of a

  10. * Zero or more repetitions

  11. + One or more repetitions

    eg. [abc]+ means >=1 occurance of a or b or c

  12. ? Optional

    eg. ab?c matches abc or ac

  13. \s any Whitespace

  14. \t any tab

  15. \n any new line

  16. ^…$ Starts and ends

  17. () capture Group

  18. (a(bc)) capture Sub group

    eg. ^(IMG\d+).png$ matches an image file name

  19. (.*) capture Variable content

  20. (a|b) Matchs a or b

  21. metacharacters

    1. \w any Alphanumeric character

    2. \W any Non-alphanumeric character

    3. \d any Digit

    4. \D any Non-digit character

    5. \s any Whitespace

    6. \S any Non-whitespace character

  22. Last but not least: .* matches anything