how to trim file - remove the columns with the same value

Question

I would like your help on trimming a file by removing the columns with the same value.

# the file I have (tab-delimited, millions of columns)
jack 1 5 9
joh         


        

Answer 1

#!/usr/bin/perl
$/="\t";
open(R,"<","/tmp/filename") || die;
while ()
{
  next if (($. % 4) == 3);
  print;
}

Well, this was assuming it was the third column. If it is by value:

#!/usr/bin/perl
$/="\t";
open(R,"<","/tmp/filename") || die;
while ()
{
  next if (($_ == 5);
  print;
}

With the question edit, OP's desires become clear. How about:

#!/usr/bin/perl
open(R,"<","/tmp/filename") || die;
my $first = 1;
my (@cols);
while ()
{
  my (@this) = split(/\t/);
  if ($. == 1)
  {
    @cols = @this;
  }
  else
  {
    for(my $x=0;$x<=$#cols;$x++)
    {
      if (defined($cols[$x]) && !($cols[$x] ~~ $this[$x]))
      {
        $cols[$x] = undef;
      }
    }
  }
  next if (($_ == 5));
#  print;
}
close(R);
my(@del);
print "Deleting columns: ";
for(my $x=0;$x<=$#cols;$x++)
{
  if (defined($cols[$x]))
  {
    print "$x ($cols[$x]), ";
    push(@del,$x-int(@del));
  }
}
print "\n";

open(R,"<","/tmp/filename") || die;
while ()
{
  chomp;
  my (@this) = split(/\t/);

  foreach my $col (@del)
  {
    splice(@this,$col,1);
  }

  print join("\t",@this)."\n";
}
close(R);