Regular Expressions.md

Regular Expressions

Replacement expressions

Convert to lower/uppercase (SO)

\L converts following characters to lowercase, \U to uppercase, and \E switches back to the original case.

\L\1\E

\.get(\w)
.\L$1

e.g. to remove the get prefix and next char to lowercase: match \.get(\w) then replace with .\L$1

Or in sed (SO, SO):

sed -r 's/(^.*)/\L\1/'

Ignore escaped quotes within quotes:

(SO)

Good: "([^"\\]|\\.)*" Version 1: Works correctly but is not terribly efficient.

Better: "([^"\\]++|\\.)*" or "((?>[^"\\]+)|\\.)*" Version 2: More efficient if you have possessive quantifiers or atomic groups (See: sin's correct answer which uses the atomic group method).

Best: "[^"\\]*(?:\\.[^"\\]*)*" Version 3: More efficient still. Implements Friedl's: "unrolling-the-loop" technique. Does not require possessive or atomic groups (i.e. this can be used in Javascript and other less-featured regex engines.)