CODEWITHSUNDEEP
perlmultiple-columnstext-processing
Davide Lorino
Davide Lorino

Reputation: 915

Sum values in second column in a text file

I have a text file with the following format:

1 4730 1031782 init
4 0 6 events
2190 450 0 top
21413 5928 1 sshd
22355 1970 2009 find

I need to sum the second column of data and return that value to the user.

My current attempt reads the data from the text file like so:

sub read_file{
  my $data_failed = 1;
  my $file = 'task_file';
  if (-z $file){print "No tasks found\n";}
  if(open (INFILE, "task_file" || die "$!\n")){
    my @COLUMNS = qw( memory cpu program );
    my %sort_strings = ( program => sub { $a cmp $b } );

    my (%process_details, %sort);

    while (<INFILE>) {
      $data_failed = 0;
      my ($process_id, $memory_size, $cpu_time, $program_name) = split;
      $process_details{$process_id} = { memory  => $memory_size,
                                        cpu     => $cpu_time,
                                        program => $program_name };
      undef $sort{memory}{$memory_size}{$process_id};
      undef $sort{cpu}{$cpu_time}{$process_id};
      undef $sort{program}{$program_name}{$process_id};
    }

    for my $column ($COLUMNS[2]) {
      my $cmp = $sort_strings{$column} || sub { $a <=> $b };
      for my $value (sort $cmp keys %{ $sort{$column} }
      ) {
          my @pids = keys %{ $sort{$column}{$value} };
          say join ' ', $_, @{ $process_details{$_} }{@COLUMNS}
              for @pids;
      }
  }
  if($total_memory_size == 1){
    sum_memory_size();
  }
} else { print "No tasks found"}
}

And my attempt to sum the values:

sub sum_memory_size{
  my @do_sum = qw(memory_size);

my $column;
my $value;

for $column (keys %{ $sort{$column}{$value} }) {
    my $found;
    my $sum = 0;
    for $value (@do_sum) {
        next unless exists $sort{$column}{$value};
        $sum += $hash{$column}{$value};
        delete $hash{$column}{$value};
        $found = 1;
    }
    $sort{$column}{somename} = $sum if $found;
}

print $sum;
}

Upvotes: 0

Views: 94

Answers (2)

choroba
choroba

Reputation: 241758

Use sum form List::Util:

use List::Util qw{ sum };

# ...

my $memory_sum = sum(map $_->{memory}, values %process_details);

Upvotes: 1

cxw
cxw

Reputation: 17041

The question describes a simple task, which appears to be part of a larger problem. One answer to the simple task is:

perl -ne '@fields=split; $sum+=$fields[1]; END { print "$sum\n" }' foo.txt

For each line (-ne), split it and add the second value ($fields[1]) to a running $sum. Then, after all lines have been processed (END), print the sum. I get 13078 from the program, which is also what I get from a calculator on the input above :) (4730 + 0 + 450 + 5928 + 1970).

Upvotes: 1

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