Using Perl, how can I sort an array using the value of a number inside each array element?

Question

Let's say I have an array, @theArr, which holds 1,000 or so elements such as the following:

01  '12 16 sj.1012804p1012831.93.gz'
02  '12 16 sj.1012832p1012859.94.gz'
03  '12 16 sj.1012860p1012887.95.gz'
04  '12 16 sj.1012888p1012915.96.gz'
05  '12 16 sj.1012916p1012943.97.gz'
06  '12 16 sj.875352p875407.01.gz'
07  '12 16 sj.875408p875435.02.gz'
08  '12 16 sj.875436p875535.03.gz'
09  '12 16 sj.875536p875575.04.gz'
10  '12 16 sj.875576p875603.05.gz'
11  '12 16 sj.875604p875631.06.gz'
12  '12 16 sj.875632p875659.07.gz'
13  '12 16 sj.875660p875687.08.gz'
14  '12 16 sj.875688p875715.09.gz'
15  '12 16 sj.875716p875743.10.gz'
...

If my first set of numbers (between the 'sj.' and the 'p') was always 6 digits, I wouldn't have a problem. But, when the numbers roll over into 7 digits the default sort stops working as the larger 7 digit numbers comes before the smaller 6 digit number.

Is there a way to tell Perl to sort by that number inside the string in each array element?

Answer 1

Looks like you need a Schwartzian Transform:

#!/usr/bin/perl

use strict;
use warnings;

my @a = <DATA>;

print 
    map  { $_->[1] }                #get the original value back
    sort { $a->[0] <=> $b->[0] }    #sort arrayrefs numerically on the sort value
    map  { /sj\.(.*?)p/; [$1, $_] } #build arrayref of the sort value and orig
    @a;

__DATA__
12 16 sj.1012804p1012831.93.gz
12 16 sj.1012832p1012859.94.gz
12 16 sj.1012860p1012887.95.gz
12 16 sj.1012888p1012915.96.gz
12 16 sj.1012916p1012943.97.gz
12 16 sj.875352p875407.01.gz
12 16 sj.875408p875435.02.gz
12 16 sj.875436p875535.03.gz
12 16 sj.875536p875575.04.gz
12 16 sj.875576p875603.05.gz
12 16 sj.875604p875631.06.gz
12 16 sj.875632p875659.07.gz
12 16 sj.875660p875687.08.gz
12 16 sj.875688p875715.09.gz
12 16 sj.875716p875743.10.gz

Answer 2

You can use a regex to pull the number out of every line inside the block you pass to the sort function:

@newArray = sort { my ($anum,$bnum); $a =~ /sj\.([0-9]+)p/; $anum = $1; $b =~ /sj\.(\d+)p/; $bnum = $1; $anum <=> $bnum } @theArr;

However, Chas. Owens's solution is better, since it only does the regex matches once for every element.