sort in perl

Shell Programming and Scripting
1

Hi

Is there any way I could reproduce the following code in perl 5.8:

sort -u FILE | sort -t: -k1,1 -k2n

which sorts by unicity first, then by first key, then by second key in numeric format.

What I have now is

@sort_array=uniq sort @sort_array;

after the contents of my file have been loaded into this array. In clear, I lack the numeric sort on the second key.

Any thought?
Cheers

2

Not terribly easy.
First, for uniqueness:

my $prev;
@uniq_array=grep { if (defined $prev && $_ eq $prev) { 0; } else { $prev=$_; 1; } } @sort_array;

Second, build yourself a little sort function:

sub sort_special { 
  @a=split(":",$a);
  @b=split(":",$b);
  $a[0] cmp $b[0] || $a[1] <=> $b[1];
}

@sort_array=sort sort_special @uniq_array;
3

my %seen = ();
my @unique = grep { ! $seen{ $_ }++ } @array;

perlfaq4 - perldoc.perl.org

4

A cached key sort should be more efficient but unless there is a lot of data to sort it might not make much difference. The code is rather cyrptic to the casual perl coder but it just strings together list functions to produce the list:

my %seen;
my @unique_sorted = map { "$_->[0]:$_->[1]" }
                 sort { $a->[0] cmp $b->[0] || $a->[0] <=> $b->[0] }
                 map { [split/:/] }
                 grep{! $seen{$_}++ } @unsorted;

Assumes all the data is in @unsorted and you don't need to do any other pre processing. Also, untested code.

5

Pretty cool. slight correction:

should be

                 sort { $a->[0] cmp $b->[0] || $a->[1] <=> $b->[1] }
6

oops.... thanks! :b: