正则表达式，用于匹配以模式开头但不以模式结尾的字符串

Question

Given a url, i have to match that the url starts with certain domain and not ends with certain pattern.
For eg,
Given a list of urls i want to match a url that starts with "http://www.google.com/" or "http://www.facebook.com/" and not ends with ".jpg" and ".bmp" and ".png"

I tried something like

^(http://www\.google\.com/|http://www\.facebook\.com/).*(\.(?!png)|(?!bmp)|(?!jpg))$

But it doesn't seem to work.. Any Mistakes in it? Or Any alternate way?

Answer 1

Something like (?!png)$ is, in general, pretty meaningless; it means "a position that is not followed by png , and that is at the end of the string", but of course the end of a string is never followed by png anyway, so (?!png)$ is equivalent to just $ . (Do you see what I mean?)

Java regexes, fortunately, support zero-width lookbehind assertions, so you can write:

^http://www\.(google|facebook)\.com.*(?<!\.(png|bmp|jpg))$

where (?<!...) means "a position that is not preceded by ... ". (See the Javadoc for java.util.regex.Pattern .)

Answer 2

This regex should work:

^https?:\/\/(?:www\.)?(?:google|facebook)\.com\/(?!.*?\.(?:jpe?g|png|bmp|gif)$).*$

Live Demo: http://www.rubular.com/r/V0X6ve1iUT

Java Demo: http://ideone.com/TlCyTG

Answer 3

试试这是您想要的确切要求

^(http://www\.google\.com/|http://www\.facebook\.com/)(?!.*?\.(?:jpe?g|png|bmp|gif)$).*$