Lessons · Regex · greedy vs lazy

Greedy takes all it can

* and + match as much as possible; adding ? (.*?) makes them stop at the first chance.

Hone is a place to practise programming. This is one of its lessons, written out in full and free to read without an account.

What it is for

Extracting the first quoted string or the first tag from a line with several.

How to think about it

Where should the match stop? If your match runs past where you meant it to stop, make the quantifier lazy, or use a negated class like [^"]* that cannot cross the delimiter.

Worked example

pattern: "(.*)"

Greedy.

text: say "hi" and "bye"

Captures: hi" and "bye. Too much.

pattern: "(.*?)"

Lazy: captures hi.

pattern: "([^"]*)"

Same result, and faster: cannot cross a quote.

Your turn

First bold tag only.

<b>.*</b>

The trap

Lazy is not 'shortest overall'; it is 'shortest from where it started'. Combined with anchors it can still surprise.

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