negated word issue

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

I'm trying to match a line which has a set pattern but only match it if a particular word doesn't appear in the rest of the line.

If this word my3.exe appears in the line I wish to skip it.

This is the original code

if (/my background error (\d+): (.+)/ ) {
   do something with the matched line
}
[download]

This is how I changed it

if (/my background error (\d+): (.+(?!my3\.exe))/ ) {
   do something with the matched line
}
[download]

It is still however picking up the records that have "my background error" and "my3.exe" in them. Can somebody pinpoint what I am doing wrong ?

Comment on negated word issue Select or Download Code

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Re: negated word issue by davido (Cardinal) on Mar 01, 2012 at 13:51 UTC
Go easy on yourself: `if( ! /my3\.exe/ and /my background error (\d+): (.+)/ ) { # do something with $1 and $2 }` [download] Sometimes breaking it into two separate problems is the clearer solution. Dave	[reply] [d/l]
Re^2: negated word issue by Anonymous Monk on Mar 01, 2012 at 14:01 UTC
Agreed this is the simplest approach. thanks	[reply]
Re: negated word issue by kcott (Archbishop) on Mar 01, 2012 at 14:20 UTC
Changing your regex to `/my background error (\d+):(?!.+my3\.exe)/` [download] seems to capture what you're after. Here's a few tests: `$ perl -Mstrict -Mwarnings -E 'while (<>) { if (/my background error ( +\d+):(?!.+my3\.exe)/ ) { say $1 } }' blah blah my background error 1234: blah blah 1234 blah blah my background error 1234: blah blah my3.exe blah blah blah my background error 1234: blah blah my4.exe blah 1234 blah blah my background error 1234: my3.exe blah blah my background error 1234:my3.exe 1234 ^C` [download] Note the last one with `1234:my3.exe` is a match: which seems to follow the pattern you're describing. If you don't want that line either, use `.` instead of `.+`, i.e. change `(?!.+my3\.exe)` to `(?!.my3\.exe)`. UPDATE I noticed you wanted to capture the text after the error number as well as that number. The solution above doesn't do that. The following regex will: `/my background error (\d+): ((?!.my3\.exe).+)/` [download] Retested: $ perl -Mstrict -Mwarnings -E 'while (<>) { if (/my background error ( +\d+): ((?!.my3\.exe).+)/ ) { say qq{$1 = \"$2\"} } else { say q{NO M +ATCH} } }' blah blah my background error 1234: blah blah 1234 = "blah blah" blah blah my background error 1234: blah blah my3.exe blah NO MATCH blah blah my background error 1234: blah blah my4.exe blah 1234 = "blah blah my4.exe blah" blah blah my background error 1234: my3.exe NO MATCH blah blah my background error 1234:my3.exe NO MATCH blah blah my background error 1234: my4.exe 1234 = "my4.exe" ^C [download] -- Ken	[reply] [d/l] [select]
Re^2: negated word issue by Anonymous Monk on Mar 01, 2012 at 17:25 UTC
Thanks. I was still trying to figure this out when you posted the update.	[reply]