How would I match the text that's after "#ab cd ef#" and before "#qr
st uv#" in the following string? I want to use a regular expression
that has both a look-behind and a look-ahead together. Is this
possible?
#ab cd ef#gh ij kl#qr st uv#
dan.j.weber@gmail.com writes:
> I want to use a regular expression that has both a look-behind and a
> look-ahead together. Is this possible?
AFAIK, yes. Just try it.
--
Joost Diepenmaat | blog: http://joost.zeekat.nl/ | work: http://zeekat.nl/
dan.j.weber@gmail.com wrote in
news:1421afb9-6b66-45d8-ba6f-60aad330f718
@p39g2000prm.googlegroups.co
m:
> How would I match the text that's after "#ab cd ef#" and before
> "#qr st uv#" in the following string? I want to use a regular
> expression that has both a look-behind and a look-ahead together.
> Is this possible?
>
> #ab cd ef#gh ij kl#qr st uv#
I may be misunderstanding the question, but I am not sure why you
think you need look-ahead or look-behind here.
#!/usr/bin/perl
use strict;
use warnings;
my $x = q{#ab cd ef#gh ij kl#qr st uv#};
if ( $x =~ /#ab cd ef#(.+)#qr st uv#/ ) {
print "$1\n";
}
# You could also use split:
print( (grep length, split /#/, $x)[1], "\n" );
__END__
--
A. Sinan Unur <1usa@llenroc.ude.invalid>
(remove .invalid and reverse each component for email address)
comp.lang.perl.misc guidelines on the WWW:
http://www.rehabitation.com/clpmisc/
dan.j.weber@gmail.com wrote:
> How would I match the text that's after "#ab cd ef#" and before "#qr
> st uv#" in the following string? I want to use a regular expression
> that has both a look-behind and a look-ahead together. Is this
> possible?
>
> #ab cd ef#gh ij kl#qr st uv#
I don't know what problems you are anticipating, so I'll just try doing it
in a straightforward manner:
use strict;
"#ab cd ef#gh ij kl#qr st uv#" =~
/(?<=#ab cd ef#)(.*?)(?=#qr st uv#)/ or die;
print $1
__END__
gh ij kl
Yep, seems to work. Which is what I expected, because the parts of Perl's
regex language are supposed to work when used together--if they didn't
there wouldn't be much point in having such a language. Neither look ahead
nor look behind claim to be an experimental features, so I'd just
storm ahead and use them with confidence.
Xho
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On Apr 9, 3:18=A0pm, xhos...@gmail.com wrote:
> dan.j.we...@gmail.com wrote:
> > How would I match the text that's after "#ab cd ef#" and before "#qr
> > st uv#" in the following string? I want to use a regular expression
> > that has both a look-behind and a look-ahead together. Is this
> > possible?
>
> > #ab cd ef#gh ij kl#qr st uv#
>
> I don't know what problems you are anticipating, so I'll just try doing it=
> in a straightforward manner:
>
> use strict;
> "#ab cd ef#gh ij kl#qr st uv#" =3D~
> =A0 =A0 /(?<=3D#ab cd ef#)(.*?)(?=3D#qr st uv#)/ or die;
> print $1
> __END__
> gh ij kl
>
> Yep, seems to work. =A0Which is what I expected, because the parts of Perl=
's
> regex language are supposed to work when used together--if they didn't
> there wouldn't be much point in having such a language. =A0Neither look ah=
ead
> nor look behind claim to be an experimental features, so I'd just
> storm ahead and use them with confidence.
>
> Xho
>
> --
> --------------------http://NewsReader.Com/------------------ --
> The costs of publication of this article were defrayed in part by the
> payment of page charges. This article must therefore be hereby marked
> advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate=
> this fact.
Thanks for your responses. The example I gave was a simplification.
The problem was that I was using (.*) instead of (.*?) and I'm not
100% why, but it doesn't work like that. Thanks.
In article
> On Apr 9, 3:18 pm, xhos...@gmail.com wrote:
> > dan.j.we...@gmail.com wrote:
> > > How would I match the text that's after "#ab cd ef#" and before "#qr
> > > st uv#" in the following string? I want to use a regular expression
> > > that has both a look-behind and a look-ahead together. Is this
> > > possible?
> >
> > > #ab cd ef#gh ij kl#qr st uv#
> >
> > I don't know what problems you are anticipating, so I'll just try doing it
> > in a straightforward manner:
> >
> > use strict;
> > "#ab cd ef#gh ij kl#qr st uv#" =~
> > /(?<=#ab cd ef#)(.*?)(?=#qr st uv#)/ or die;
> > print $1
> > __END__
> > gh ij kl
> >
> > Yep, seems to work. Which is what I expected, because the parts of Perl's
> > regex language are supposed to work when used together--if they didn't
> > there wouldn't be much point in having such a language. Neither look ahead
> > nor look behind claim to be an experimental features, so I'd just
> > storm ahead and use them with confidence.
>
> Thanks for your responses. The example I gave was a simplification.
> The problem was that I was using (.*) instead of (.*?) and I'm not
> 100% why, but it doesn't work like that. Thanks.
Xho's example works either with (.*?) or (.*), so your problem may lie
elsewhere. The only difference would be if your string included two
'#qr st uv#' substrings after the initial '#ab cd ef#'. In that case
(.*?) will match the shortest possible string, while (.*) will match
the longest.
--
Jim Gibson
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