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I need a regex to return true for 01.mp4

Answer 1

+6 A:

Try this:

/^[0-9]{1,2}\.(?:mp4|mpg|avi)$/

Kerry 2010-06-08 08:00:55

can you tell me what does ?: do here, i what i think is that is somehow limits the characters of extension

Umair 2010-06-08 08:12:18

To explain: the square brackets, `[]`, denote a character class; `[abc]` means "match either `a` or `b` or `c`", and `[a-z]` means "match any character between `a` and `z`". Thus, `[mp4|mpg|avi]` matches *any of those characters*, the order being irrelevant. Parentheses, `()`, group regular expressions, which is what you want to do. The `?:` bit tells the regex engine not to allocate a capturing group for that set of parentheses, otherwise it would be accessible with `$1`.

Antal S-Z 2010-06-08 08:18:49

oh alright, if I am not wrong then this simply means that () match exactly whats given, while having ?: or not wont matter that much

Umair 2010-06-08 08:22:05

Yes, in a way; you get a slight performance benefit if you use `(?:...)`, and it might help later on in regexes where you have several capturing groups and several non-capturing groups to keep the numbering of backreferences simple. Apart from that, `(...)` will match exactly the same as `(?:...)`.

Tim Pietzcker 2010-06-08 13:05:51

Answer 2

A:

/^[0-9]{1,2}\.[mp4|mpg|avi]?/

turbod 2010-06-08 08:01:02

That would make the extension optional (but non repeating), but it wouldn't solve the original problem.

Thorarin 2010-06-08 08:06:13

How is it different from OP's regex and how does it solve the problem - you're confused between parenthetic groups `()` and character class `[]`

Amarghosh 2010-06-08 08:08:34

Answer 3

A:

I played a bit with my original regex and came up with this

/^[0-9]{1,2}\.[mp4|mpg|avi]{3}$/

and this works like a charm :)

Umair 2010-06-08 08:11:30

Try `11.mmm`. _

KennyTM 2010-06-08 08:21:31

thak you for pointing this out Kenny, it didnt work indeed

Umair 2010-06-08 08:26:35

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I need a regex to return true for 01.mp4

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