Comments on: Not Substring Regular Expressions

By: Neil Greenwood

Neil Greenwood — Fri, 23 Feb 2007 08:59:42 +0000

I think Minute Bol’s second suggestion above uses Java RegEx’s negative look-behind assertion. My copy of “Java in a Nutshell (4th ed)” says that the pattern “must be a…fixed number of characters”, so I don’t think his suggestion will work exactly. There’s no such restriction on the negative look-ahead assertion, but I can’t think how to re-write the regex that way.

HTH. Hwyl,
Neil.

By: Peter

Peter — Tue, 20 Feb 2007 09:19:07 +0000

Something like this should be ok

(lets see if a pre tag can help me)

while( $html =~/
(
]* #0 or more non >
\s+alt\s*= #and an alt attribute
)
[^>]* #instead followed by 0 or more non >
> #and a tag close
)/xg)
{
print $1.”\n\n”;
}

By: Peter

Peter — Tue, 20 Feb 2007 09:18:20 +0000

Something like this should be ok

while( $html =~/
(
]* #0 or more non >
\s+alt\s*= #and an alt attribute
)
[^>]* #instead followed by 0 or more non >
> #and a tag close
)/xg)
{
print $1.”\n\n”;
}

By: Ed Davies

Ed Davies — Tue, 20 Feb 2007 00:21:43 +0000

What am I missing? XPath?

Sorry, couldn’t help it.

By: Minute Bol

Minute Bol — Mon, 19 Feb 2007 18:48:33 +0000

hey rusty - no ‘preview’ button? let’s try that again:
(?!]*\salt[^=>]*=[^>]*>)]*>
matches the thing and then makes sure there was no ‘ alt=’ in the match, or something to that effect

By: Minute Bol

Minute Bol — Mon, 19 Feb 2007 18:46:28 +0000

yeah that’s a good one. here’s what i came up with:
(?!]*\salt[^>]*>$)]*>
seems to work.

By: Xan Gregg

Xan Gregg — Mon, 19 Feb 2007 18:29:41 +0000

This works pretty well for me (in BBEdit), ignoring case:

a]|a[^l]|al[^t]|”.*”|’.*’)*?>

It allows
any character not a ‘>’ or ‘a’
any ‘a’ not followed by an ‘l’
any ‘al’ not followed by an ‘t’
anything in quotes

So it disallows ‘alt’ outside of quotes. Will give a false results for any other tags containing ‘alt’.

You might also want to search for: alt=”".