Read the file using a CPAN module (e.g. Text::CSV), and keep a hash or array that, for each unique ID, records the length of the string in column 2, and the entire corresponding row. (A hash would be more natural, I think, since you could index it by unique ID; an array would allow you to easily preserve the ordering of rows from the original file, in case that's important).

Here's a hash-based solution: 

#!/usr/bin/perl

use strict;
use warnings;
use feature qw/say/;

use Text::CSV;

my $csv = Text::CSV->new( { binary => 1 })
    or die "Cannot use CSV" . Text::CSV->error_diag();

my %results = ();

while(<DATA>) {
    chomp;

    $csv->parse($_) or die "Could not parse string '$_'" . Text::CSV->
+error_diag();
    my @row = $csv->fields();

    my $uniqueID = $row[0];
    my $string   = $row[1];

    if(!exists $results{$uniqueID} or $results{$uniqueID}->{'length'} 
+> length $string) {
        $results{$uniqueID} = {
            'length'    => length $string,
            'row'       => $_
        };
    }
}

foreach (sort keys %results) {
    say $results{$_}->{'row'};
}


__DATA__
A, texttexttext, col3, col4,
B, textt,        col3, col4,
A, text,         col3, col4,
B, texttex,      col3, col4,

[download]

I'm reading from __DATA__ here; to use an external file, simply use the magic filehandle, <>, instead of <DATA>. This'll allow you to specify files on the command line as well as pipe them into the script: 

$ perl script.pl data.csv
...
$ generate_csv | perl script.pl
...
$

[download]

Side note -- I see you crossposted your question to StackOverflow. That's fine, of course, but it's generally considered polite to inform people of crossposting to avoid duplicated/unnecessary effort.

In reply to Re: Find the row with shortest string for a given input in a csv file. by AppleFritter
in thread Find the row with shortest string for a given input in a csv file. by Anonymous Monk

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