Help with Regex: (Absolute/Relative URLs)

OverlordQ has asked for the wisdom of the Perl Monks concerning the following question:

I have a script, which grabs a webpage, parses it and changes a few urls, then displays the result to the browser, all of it works, except one part of the parsing:

        $text =~ s#src=\"(.*?)\"#src=\"$url$1\"#sig;
[download]

$url contains the orginal URL which was grabbed. Here-in lies the problem:
Assume $url is http://www.slashdot.org. If the URL in the src tag was:

http://www.slashdot.org/image.gif

it get's changed into:

http://www.slashdot.orghttp://www.slashdot.org/image.gif

but if the url was a relative url:

image.gif

becomes:

http://www.slashdot.org/image.gif

which works. So my question/problem, is there any way to get the regex to ignore absolute urls?

Comment on Help with Regex: (Absolute/Relative URLs) Select or Download Code

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•Re: Help with Regex: (Absolute/Relative URLs) by merlyn (Sage) on Aug 05, 2003 at 21:04 UTC
Yes, stop doing it that way. Use URI to turn relative URLs into absolute URLs. I have a few examples in my columns. -- Randal L. Schwartz, Perl hacker Be sure to read my standard disclaimer if this is a reply.	[reply]
Re: •Re: Help with Regex: (Absolute/Relative URLs) by OverlordQ (Hermit) on Aug 05, 2003 at 21:52 UTC
Although Abigail-II's regex below works, after looking over the code and the URI docs, I think it could use a good re-write using URI instead. edit: example script	[reply]
Re: Help with Regex: (Absolute/Relative URLs) by Abigail-II (Bishop) on Aug 05, 2003 at 21:41 UTC
`$text =~ s#src="(?!\w+://)([^"])"#src="$url$1"#ig;` [download] There's no need to escape the quotes, and it's more efficient to change the `.?` to `[^"]*`. Then you don't need the `/s` either. Abigail	[reply] [d/l] [select]
Re: Re: Help with Regex: (Absolute/Relative URLs) by OverlordQ (Hermit) on Aug 05, 2003 at 21:48 UTC
Ah, thank you. It's been ~2-3 years since the script has been written, so many reasons for doing it that way are probably forgotten.	[reply]