grep a specific strings in a Perl array

Question

How to grep only multiple sets of five characters in any order in an array in a Perl program?

@arr2 = grep(/[BCRZ]+/, @arr1);

@arr1 can contain

CRZBBZTCCBBRZ
FJDLSFJSLFJS
CRZBBZCCBBRZ

only the lines like the last should be taken

I don't understand why the first line should be excluded. And where are your five characters? Do you mean the string has to contain at least five of BCRZ? — Borodin
– Borodin, Commented May 16, 2014 at 14:31
I missed the 5th letter. Let's take some thing different from T like W. In this case, the 1st and 2nd should be discarded. Any set of 5, CBRZW in any order in any length is accepted — carol
– carol, Commented May 16, 2014 at 14:35

Len Jaffe · Accepted Answer · 2014-05-16 14:53:56Z

3

If what is you want is lines that only contain the 5 chars and none others, then a regex like:

 /^[BRCZW]+$/

looks for strings containing one or more of your 5-character set, but containing no other characters. But it might be more efficient to us @carol's solution using grep(). Which uses a regex to determine if the string has any of the unwanted characters, and then rejects that line.

answered May 16, 2014 at 14:53

Len Jaffe

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2 Comments

Tom Fenech Over a year ago

As I suggested in the comments below @Borodin's answer, this could be used in exactly the same way inside a grep. How were you suggesting it could be used instead?

Len Jaffe Over a year ago

I don't think your answer was in my feed when I typed mine. But yes, I am suggesting the same thing as you.

Borodin · Accepted Answer · 2014-05-16 14:59:52Z

3

I think this may do what you want. It rejects a string if it contains any character other than CBRZW.

use strict;
use warnings;

my @arr1 = qw/ CRZBBZTCCBBRZ FJDLSFJSLFJS CRZBBZCCBBRZ /;

my @arr2 = grep { not /[^CBRZW]/ } @arr1;

print "$_\n" for @arr2;

output

CRZBBZCCBBRZ

edited May 16, 2014 at 14:59

answered May 16, 2014 at 14:34

Borodin

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3 Comments

carol Over a year ago

but it seems that with "not", it holds any thing except BCRZ, no? which is the opposite of what I want

Tom Fenech Over a year ago

@carol this is a double negative - there's the not and the ^ in the character class. Another way you could do this is with grep { /^[BCRZ]+$/ } @arr1; - one or more characters from that class between the start and end of the string.

Borodin Over a year ago

@carol: Tom is correct. As I wrote, the code rejects a string if it contains any character other than CBRZW. Also, the code produces the output that you requested.

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