regex

Question 1

.

Answer 1

anything, except line breaks

Question 2

\d

Answer 2

digit in 0123456789

Question 3

\D

Answer 3

non-digit

Question 4

\w

Answer 4

“word” (letters and digits and _)

Question 5

\W

Answer 5

non-word

Question 6

space

Answer 6

space

Question 7

\t

Answer 7

tab

Question 8

\r

Answer 8

return

Question 9

\n

Answer 9

new line

Question 10

\s

Answer 10

whitespace (any of tab, return, new line, space)

Question 11

\S

Answer 11

non-whitespace

Question 12

[…]; [aeiou]; [^aeiou]

Answer 12

character class; vowels; non-vowels (incl non-letters!)

Question 13

[a-e] [x-y] [0-9]; [a-e0-9]

Answer 13

range of letters / numbers; abcde0123456789

Question 14

\b

Answer 14

word boundary

Question 15

\B

Answer 15

non-word boundary

Answer 16

beginning of line

Question 17

$

Answer 17

end of line

Question 18

(X|Y)

Answer 18

X or Y

Question 19

X*

Answer 19

0 or more repetitions of X (wut? 0?)

Question 20

X+

Answer 20

1 or more repetitions of X

Question 21

X?

Answer 21

0 or 1 instances of X

Question 22

X{m}

Answer 22

exactly m instances of X

Question 23

X{m,}

Answer 23

at least m instances of X

Question 24

X{m,n}

Answer 24

between m and n (inclusive) instances of X

Question 25

ab+ / (ab)+ – what’s the difference?

Answer 25

ab+ matches ab, abb, abbb, etc. (ab)+ matches ab, abab, ababab…

Question 26

Characters that should be escaped () to match:

Answer 26

{} [] () ^$ . | * + ? \ (and - inside [ ]). . matches the period, \ matches the backslash