regex picking out a particular string

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

Hello Monks,

Please tell me what might be wrong with my regex:

My string is:

$string = "hello = 1234ab;cat;dog;4892";
[download]

I want to grab everything between the 2nd the and 3rd semicolons...

my $semiColon=2;
if ( $string =~ /hello.*=(\s*.*;\s*){$semiColon}(\s*.*;\s*).*/i )

my $substring = $2;
[download]

The $substring should print out dog, but instead it grabs all the string.

Thanks a lot in advance

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Re: regex picking out a particular string by BUU (Prior) on Feb 04, 2005 at 02:10 UTC
Heres a better way: `my $substring = (split( ';', $string))[2];` [download]	[reply] [d/l]
Re^2: regex picking out a particular string by Anonymous Monk on Feb 04, 2005 at 13:21 UTC
Thank you all...that does help	[reply]
Re^2: regex picking out a particular string by nobull (Friar) on Feb 04, 2005 at 20:07 UTC
`my $substring = (split( ';', $string))[2];` [download] A regular expression should look line a regular expression. `my $substring = (split( /;/, $string))[2];` [download]	[reply] [d/l] [select]
Re: regex picking out a particular string by Roy Johnson (Monsignor) on Feb 04, 2005 at 01:59 UTC
Works for me: `use strict; use warnings; my $string = "hello = 1234ab;cat;dog;4892"; my $semiColon=2; if ( $string =~ /hello.=(\s.;\s){$semiColon}(\s.;\s)./i ) { my $substring = $2; print "$substring\n"; }` [download] I would recommend that you at least modify your dot-stars to be `.?` (non-greedy). And get rid of the trailing one. That one's useless. `/hello.?=(\s.?;\s){$semiColon}(\s.?;\s)/i` [download] Caution: Contents may have been coded under pressure.	[reply] [d/l] [select]
Re: regex picking out a particular string by gube (Parson) on Feb 04, 2005 at 04:00 UTC
Hi, try this in regex; `$string = "hello = 1234ab;cat;dog;4892"; $string =~ m#([^;]?)\;([^;]?);([^;]*?);#gsi; print $3; o/p:Dog` [download] Regards, Gubendran.l	[reply] [d/l]
Re: regex picking out a particular string by nobull (Friar) on Feb 04, 2005 at 20:17 UTC
It has been pointed out that you should use `split()` but if you'd rather use match: `my $semiColon=2; my ($substring) = $string =~ /(?:;.?){$semiColon}(.?);/;` [download] If you want to find the n^th piece of a m-piece string where n << m it can make sense to use the match approach. Note: $substring will be undef is $string contained fewer then $semiColon+1 semicolons. Update: Correction, I meant where n and m are both large. If n is small then simply use the LIMIT arg of split!	[reply] [d/l] [select]