Regex problem, match if line contains <a>, unless it also contains <b>

**toylet** · Jul 19 '05, 04:56 AM

Re: Regex problem, match if line contains <a>, unless it also contains<b&g t;

shouldn't it be ".*$search2 ?" rather than "?.*$search 2" ?
[color=blue]
> I'm creating my regex like this:
> $compiled_regex = qr/^(?!.*$search2) $search1(?!.*$s earch2)/;[/color]

--
.~. Might, Courage, Vision. In Linux We Trust.
/ v \ http://www.linux-sxs.org
/( _ )\ Linux 2.4.22-xfs
^ ^ 4:14pm up 5:47 1 user 1.01 1.00

**James Dyer** · Jul 19 '05, 04:56 AM

Re: Regex problem, match if line contains <a>, unless it also contains <b>

OK, I was being stupid, and really not thinking about what my regex
was actually doing.
I've now solved the problem - for those of you who are interested,
this appears to work:

$compiled_regex = qr/^(?!.*$search2) .*$search1/;

J

jad@hungover.or g (James Dyer) wrote in message news:<392df3a3. 0402190543.80b2 2ea@posting.goo gle.com>...[color=blue]
> I'm having problems getting a regex to work.
> Basically, given two search parameters ($search1 and $search2), it
> should allow me to filter a log file such that lines with the $search1
> string in are printed, unless the $search2 string is also in that line
> somewhere (either before or after $search1).
>
> I'm creating my regex like this:
> $compiled_regex = qr/^(?!.*$search2) $search1(?!.*$s earch2)/;
>
> I then use it:
>
> while( <> ) {
> next if( $_ !~ /$compiled_regex/ );
> print $_ . "\n";
> }
>
> With the following test data:
>
> 2004-02-18 04:06:50 1AtIua-0001Hh-00 -> sysadmin@foobar .com R=lookuphost T=remot
> e_smtp H=mxhost-1.foo.bar [0.0.0.0]
> 2004-02-19 04:02:02 1AtfNx-0008DC-00 -> sysadmin@foobar .com R=lookuphost T=remot
> e_smtp H=mxhost-1.foo.bar [0.0.0.0]
> 2004-02-19 04:07:26 1AtfO5-0008Gs-00 -> sysadmin@foobar .com R=lookuphost T=remot
> e_smtp H=mxhost-1.foo.bar [0.0.0.0]
>
> If $search1 is set to 'sysadmin', and search2 is set to '0008Gs',
> none of the lines in the data are displayed, whereas I would expect the
> first two to be displayed.
>
> With this test data:
> foo
> foo foo
> foo foo foo
> foo bar
> bar foo
> foo bar foo
> foo bar bar
> bar foo bar
> bar foo foo
> bar
> bar bar
> bar bar bar
>
> $search1 set to 'foo', and $search2 set to 'bar', I get the
> expected results (foo, foo foo and foo foo foo displayed).
>
> I just can't figure out why nothing is being displayed in my first test case.
> My gut instinct is that it's got something to do with the special'ish
> characters in the data ('-', '>' etc.), but I'm not sure.
>
> Any thoughts?
>
> J[/color]

**toylet** · Jul 19 '05, 04:56 AM

Re: Regex problem, match if line contains <a>, unless it also contains<b&g t;

> I've now solved the problem - for those of you who are interested,[color=blue]
> this appears to work:
> $compiled_regex = qr/^(?!.*$search2) .*$search1/;[/color]

what's the meaning of "?!" in the regex?

--
.~. Might, Courage, Vision. In Linux We Trust.
/ v \ http://www.linux-sxs.org
/( _ )\ Linux 2.4.22-xfs
^ ^ 7:42pm up 9:15 1 user 0.97 0.93

**toylet** · Jul 19 '05, 04:56 AM

Re: Regex problem, match if line contains <a>, unless it also contains<b&g t;

>> I've now solved the problem - for those of you who are interested,[color=blue][color=green]
>> this appears to work:
>> $compiled_regex = qr/^(?!.*$search2) .*$search1/;[/color]
>
> what's the meaning of "?!" in the regex?[/color]

I figured it out. need to force the context of the $! variable.

print int($!) . $!;

int($i) prints the error number, 2nd $! prints the message.

--
.~. Might, Courage, Vision. In Linux We Trust.
/ v \ http://www.linux-sxs.org
/( _ )\ Linux 2.4.22-xfs
^ ^ 7:54pm up 9:27 1 user 1.00 0.94

**nobull@mail.com** · Jul 19 '05, 04:56 AM

Re: Regex problem, match if line contains <a>, unless it also contains <b>

jad@hungover.or g (James Dyer) wrote in message news:<392df3a3. 0402190543.80b2 2ea@posting.goo gle.com>...
[color=blue]
> $compiled_regex = qr/^(?!.*$search2) $search1(?!.*$s earch2)/;[/color]

Ignoring the possiblity that $search1 maches a newline, the second
(?!.*$search2) is redundant. It can never fail to match since the re
engine wouldn't get as that far if there was a match for $search2
anywhere in the data.

$compiled_regex = qr/^(?!.*$search2) $search1/s;
[color=blue]
> 2004-02-18 04:06:50 1AtIua-0001Hh-00 -> sysadmin@foobar .com R=lookuphost T=remot[/color]
[color=blue]
> If $search1 is set to 'sysadmin', and search2 is set to '0008Gs',[/color]

You are only looking for $search1 at the start of the string. You
probably wanted.

$compiled_regex = qr/^(?!.*$search2) .*$search1/s;

Note - using a single regex for this is probably not a good idea
unless you are forced into doing so by the fact that you are calling
an existing function that you can't modify and that takes a single
regex as an argument.

If you are not compelled to use a single regex it is clearer, and
probably faster to use two.

/$search1/ && !/$search2/
[color=blue]
> Any thoughts?[/color]

Well since you ask...

This topic has been frequently discussed in the Perl newsgroups that
exist on Usenet. I think you should have done a search before you
posted. Having decided you wanted to post I think you should have
done so to a newsgroup that still exists. This one doesn't (see FAQ)
so very few people will see what you post here.

Regex problem, match if line contains <a>, unless it also contains <b>

Regex problem, match if line contains <a>, unless it also contains <b>

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