Thank you so much! This answer is very clear!!
On Thu, Dec 29, 2011 at 2:03 PM, Kronheim, David (Contr)
<david.kronh...@ftr.com> wrote:
> Actually, the ending ? makes the match non-greedy, in detail:
> Given:
> SASI_Hs01_00205058 HUMAN NM_005762 857 MISSION® siRNA 2
> 140.00
> if (/(SASI\w+)(.+?)\s(\d+)\s/) { print "$3\n"; }
> Match starts looking for the literal SASI followed by one or more \w's, which
> are upper or lower case letters or digits or underscores, the charcater class:
> [a-zA-Z0-9_],
> So SASI is followed by letters, underscores or digits till the pattern finds
> whitespace, in .+?, '.' is any character except a newline,
> plus means one or more characters that are not newlines, the '?' means
> to match the minimal pattern/string possible,
> the maximal greedy string might grab every character up to the newline
> (if there is one) at the end of the line.
> The minimal, non-greedy match has to allow the rest of the pattern to match
> which is the one or more digits \d+ surronded by white space.
>
> Sincerely,
> David Kronheim
> Production Support Tier II
> Gateway Error Correction, VZ450 EDI, EDI Billing, & Metakey/LIA
> 484-213-1315
> ________________________________________
> From: Chris Stinemetz [chrisstinem...@gmail.com]
> Sent: Thursday, December 29, 2011 2:45 PM
> To: Xi Chen
> Cc: beginners@perl.org
> Subject: Re: Hello a question about ".+?"
>
> On Thu, Dec 29, 2011 at 1:17 PM, Xi Chen <cxde...@gmail.com> wrote:
>> Hello everyone,
>>
>> I have a question about how to translate the meaning of ".+?". Please
>> see the examples below:
>> SASI_Hs01_00205058 HUMAN NM_005762 857 MISSION® siRNA 2
>> 140.00
>> I want to get number"857", I found the command below works:
>> perl -ne 'if (/(SASI\w+)(.+?)\s(\d+)\s/) { print "$3\n"; }'
>> but ".+" or ".*"doesn't work. I don't know why "?" is so important?
>>
>
> I believe it makes the grouping optional.
>
> Match 1 or 0 times
>
> HTH,
>
> Chris
>
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