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Re^3: Sorting files you Have read

by markh (Scribe)
on Nov 16, 2006 at 22:25 UTC ( #584619=note: print w/ replies, xml ) Need Help??


in reply to Re^2: Sorting files you Have read
in thread Sorting files you Have read

I'll modify your example code to help you do some simple sorting. Now, this is likely not the most efficient way to do it, but since you have a small dataset and you are new to perl, this can help you get started.

use strict; use warnings; open (SOMELIST, "somelist") or die "Cannot open file $!\n"; my %sort_data; while (my $record = <SOMELIST>) { my @one_line = split(/,/, $record); while (exists $sort_data{$one_line[1]}) { $one_line[1] = "$one_line[1]" . " "; #add a blank for + uniqueness } $sort_data{$one_line[1]} = $record; #store it by 2nd column } close (SOMELIST); foreach my $line (sort {$a cmp $b} keys %sort_data) { print "$sort_data{$line}"; }


Like I said, this isn't the most efficient or even best method, but it is simple enough that you can hopefully see what is going on.


(2006-11-18 17:21 GMT) Edited my perl code to remove a couple of syntax errors. - Thanks Grandfather for pointing them out.


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Re^4: Sorting files you Have read
by GrandFather (Cardinal) on Nov 16, 2006 at 23:07 UTC

    If you find yourself "uniquifying" keys for a hash you should probably be using an array. Consider:

    use strict; use warnings; use constant KEY => 1; my @sort_data; while (my $record = <DATA>) { my $key = (split(/,/, $record))[KEY]; push @sort_data, [$record, $key]; } foreach my $pair (sort {$a->[1] cmp $b->[1]} @sort_data) { print "$pair->[0]"; }

    using the same data as in previous samples prints:

    BUT, It runs with no errors, but nothing prints. I tried your code, and it seems quite simple, hence, efective. At the moment, due to the small file size, sort time is unimportant. At some point, when I get to that stage, the sorted data will be reuse +d.

    DWIM is Perl's answer to Gödel

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