negate a match in regex

Posted by ikeon on November 27, 2008, 3:40 am

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Hi All,
I have a script that I convert xml tags to html. like "<" I convert to
"<" and so on.
after the conversion I need to capture the information inside the tag.
let take for example the string "<abcd>: which is equivalent to
"<abcd>".
I tried to capture the "abcd" which can be different from tag to tag
in the following way:

/\&lt\;([^\&\gt\;]*)/

like match "<" and then match anything that is not ">".
the thing is that it doesn't work on all tags for some reason and I
was wondering on a principal base if doing a [^somestring] suppose to
work ?

Thanks.

Posted by Peter Makholm on November 27, 2008, 3:50 am

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> like match "<" and then match anything that is not ">".

> the thing is that it doesn't work on all tags for some reason and I

> was wondering on a principal base if doing a [^somestring] suppose to

> work ?

No, using [^string] wont work as you're expecting. Just like
[string] doesn't match 'string' but only one of the letters s, t, r,
i, n, or g [^stirng] just matches one letter which isn't in 'string'.

What you need is a negative look-ahead (?!string). Read 'perldoc
perlre' for the explanation of it.

//Makholm

Posted by John W. Krahn on November 27, 2008, 5:13 am

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ikeon wrote:

> I have a script that I convert xml tags to html. like "<" I convert to

> "<" and so on.

> after the conversion I need to capture the information inside the tag.

> let take for example the string "<abcd>: which is equivalent to

> "<abcd>".

> I tried to capture the "abcd" which can be different from tag to tag

> in the following way:

> /\&lt\;([^\&\gt\;]*)/

You probably want something like:

/<(.*?)>/

John
--
Perl isn't a toolbox, but a small machine shop where you
can special-order certain sorts of tools at low cost and
in short order. -- Larry Wall

Posted by ikeon on November 27, 2008, 1:30 pm

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> ikeon wrote:

> > I have a script that I convert xml tags to html. like "<" I convert to

> > "<" and so on.

> > after the conversion I need to capture the information inside the tag.

> > let take for example the string "<abcd>: which is equivalent to

> > "<abcd>".

> > I tried to capture the "abcd" which can be different from tag to tag

> > in the following way:

> > /\&lt\;([^\&\gt\;]*)/

> You probably want something like:

> /<(.*?)>/

> John

> --

> Perl isn't a toolbox, but a small machine shop where you

> can special-order certain sorts of tools at low cost and

> in short order. =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0--=

Larry Wall

The (?!string) didn't work for some reason but I have learned a lot
from "perldoc perlre" ;)
The solution was /<(.*?)>/ which is the simple one. I tried it
with only (.*) but it was "greedy".

Thanks John and Peter for your quick respone.

Posted by sln on November 28, 2008, 1:38 pm

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>Hi All,

>I have a script that I convert xml tags to html. like "<" I convert to

>"<" and so on.

>after the conversion I need to capture the information inside the tag.

>let take for example the string "<abcd>: which is equivalent to

>"<abcd>".

>I tried to capture the "abcd" which can be different from tag to tag

>in the following way:

>/\&lt\;([^\&\gt\;]*)/

>like match "<" and then match anything that is not ">".

>the thing is that it doesn't work on all tags for some reason and I

>was wondering on a principal base if doing a [^somestring] suppose to

>work ?

>Thanks.

I'm still confused with your terminology 'xml tags to html'.
So be it.

How do you go from "<abcd>" to "<abcd>" without capturing
'abcd' ?

sln

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