Pattern problem

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

I'm trying to match a pattern that contains several words but only if the 3rd word doesn't begin with a #. e.g.

sample data....

Status Host Pluto up
Host System Pluto 10.1.4.11
Host System Mars IP 10.1.3.10
Status Host Jupiter down
Host System #neptune IP 10.10.10.10
Disk load Mars imminent
Host System Venus IP 12.1.2.13.14

......
[download]

The input data can stretch to thousands of records in random sort order. I need to pick out the records which begin "Host System" but not those where the 3rd word begins with # e.g. from the above sample data I don't want

 Host System #neptune IP 10.10.10.10
[download]

But I do want

Host System Pluto 10.1.4.11
Host System Mars IP 10.1.3.10
Host System Venus IP 12.1.2.13.14
[download]

I tried doing this

if $text =~ /Host System (?!#)/ next;
[download]

This didn't work.
How do I get the pattern match to only pick up records where the 3rd field doesn't start with a # ?
bear in mind that the 3rd field can begin with pretty much any character/number

Comment on Pattern problem Select or Download Code

Replies are listed 'Best First'.
Re: Pattern problem by aquarium (Curate) on Jan 27, 2006 at 14:17 UTC
`print "match" if($text =~ /Host System [^#]/);` [download] the hardest line to type correctly is: stty erase ^H	[reply] [d/l]
Re^2: Pattern problem by ptum (Priest) on Jan 27, 2006 at 14:23 UTC
Darn those global monks! Here it is, 6:20 am local time, and I figured, heck, nobody else is awake, I'll get a chance to be the first to answer a question. But I see it is 2:20 pm your time -- this monastery never sleeps! :)	[reply]
Re: Pattern problem by japhy (Canon) on Jan 27, 2006 at 14:35 UTC
I'd like to know how you've determined `/Host System (?!#)/` doesn't work. It should work fine. `while (<FH>) { print if /^Host System (?!#)/; # or perhaps for more whitespace safety # print if /^Host\s+System\s+(?![#\s])/ }` [download] Jeff `japhy` Pinyan, P.L., P.M., P.O.D, X.S.: Perl, regex, and `perl` hacker How can we ever be the sold short or the cheated, we who for every service have long ago been overpaid? ~~ Meister Eckhart	[reply] [d/l] [select]
Re^2: Pattern problem by Anonymous Monk on Jan 27, 2006 at 14:50 UTC
Hmm this is both embarrasing and interesting at the same time. I've just redone my tests and it does work using `/Host System (?!#)/` [download] Most people seem to have suggested that it shouldn't do though based on the previous answers ??	[reply] [d/l]
Re^3: Pattern problem by mikeraz (Friar) on Jan 27, 2006 at 15:32 UTC
Nah, they just did the straightforward reply to your OQ "How do I ..." Congrats to japhy for thinking it through. Be Appropriate && Follow Your Curiosity	[reply]
Re: Pattern problem by ptum (Priest) on Jan 27, 2006 at 14:18 UTC
Maybe something as simple as this? `#!/usr/local/bin/perl use strict; while (<DATA>) { if (/Host System [^#]/) { print "$_"; } } __DATA__ Status Host Pluto up Host System Pluto 10.1.4.11 Host System Mars IP 10.1.3.10 Status Host Jupiter down Host System #neptune IP 10.10.10.10 Disk load Mars imminent Host System Venus IP 12.1.2.13.14` [download] No good deed goes unpunished. -- (attributed to) Oscar Wilde	[reply] [d/l]
Re^2: Pattern problem by mk. (Friar) on Jan 27, 2006 at 14:33 UTC
or simply `perl -ne 'print if /Host System [^#]/;' records.txt` [download] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ grrr.... argh!	[reply] [d/l]
Re^3: Pattern problem by Mago (Parson) on Jan 27, 2006 at 15:41 UTC
`perl -pe 's/(Host System [^#].+)\|.+/$1/gs' records.txt` [download] =**** Mago mago@rio.pm.org	[reply] [d/l]
Re: Pattern problem by spadacciniweb (Curate) on Jan 27, 2006 at 14:21 UTC
Why `$text =~ /Host System (?!#)/` ?? Correct: `$text =~ /Host System [^#]/`	[reply] [d/l] [select]
Re^2: Pattern problem by ikegami (Patriarch) on Jan 27, 2006 at 18:51 UTC
`$text =~ /Host System (?!#)/` is correct too. However, `[^#]` is probably faster and an acceptable replacement in this case. The problem is `if $text =~ /Host System (?!#)/ next;` was used instead of `if ($text =~ /Host System (?!#)/) { next; }` or `next if ($text =~ /Host System (?!#)/);` or `next if $text =~ /Host System (?!#)/;`	[reply] [d/l] [select]


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