Regex to match number specific number in a string

Question

I'm trying to fix a regex I create.

I have an url like this:

and I have to match the product ID (822).

I write this regex

(?<=prodotti\/).*(?<=\/)

and the result is "822/"

My match is always a group of numbers between two / /

Use a lookahead instead of a lookbehind, also use a reluctant quantifier instead of a greedy one (?<=prodotti\/).*?(?=\/). See the difference — HamZa
– HamZa, Commented Mar 27, 2014 at 9:04

ccjmne · Accepted Answer · 2014-03-27 09:09:51Z

2

You're almost there!

Simply use:

(?<=prodotti\/).*?(?=\/)

instead of:

(?<=prodotti\/).*(?<=\/)

And you're good ;)

I've actually just changed two things:

replaced that lookbehind of yours ((?<=\/)) by its matching lookahead... so it asserts that we can match a / AFTER the last character consumed by .*.
changed the greediness of your matching pattern, by using .*? instead of .*. Without that change, in case of an url that has several / following prodotti/, you wouldn't have stopped to the first one.
i.e., given the input string: http://www.demo.it/prodotti/822/Panasonic/TXP46G20E.html, it would have matched 822/Panasonic.

answered Mar 27, 2014 at 9:03

ccjmne

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4 Comments

Can you add a brief explanation... ? :)

now is ok. I'm learning regex so I want also to know what's my fault :)

Hey, you're right to ask, and actually my answer had no explanation before I edited it (within a very short time), so that was totally legitimate ;)

Don't forget to accept the answer it your problem is solved :)