greetings monks, i am trying to read 100 random lines from a big text file (536 MB) . I used this code from Perl Cookbook to do this. But i get "couldn't open file for read/write". can somebody tell me what am i doing wrong or direct me towards any other apporaches to this problem ?? here is the code i am using right now. 

#!/user/bin/perl
for ($i = 0; $i<= 10; $i++){
$roll = int (rand 453) + 1;
push (@dvdr, $roll);
}

$filename = 'dvd_subtitles_final.txt';
open (DVD, "< /home/sid/kwicionary/$filename") or die "Can't open $fil
+ename for reading: $!";

$path = "/home/sid/kwicionary/";
$indexname = "$filename.index";

sysopen(IDX,$indexname, O_CREAT|O_RDWR) or die "Can't open $indexname 
+for read/write:$!";
build_index(*DVD, *IDX) if -z $indexname;

foreach (@dvdr){
$line_number = 2;
$line = line_with_index(*ORIG,*IDX,$line_number);
die "Didn't find line $line_number in $filename" unless defined $line;
print "$_ $line \n";
}

sub build_index {
    my $data_file  = shift;
    my $index_file = shift;
    my $offset     = 0;

    while (<$data_file>) {
        print $index_file pack("N", $offset);
        $offset = tell($data_file);
    }
}
sub line_with_index {
    my $data_file   = shift;
    my $index_file  = shift;
    my $line_number = shift;

    my $size;               # size of an index entry
    my $i_offset;           # offset into the index of the entry
    my $entry;              # index entry
    my $d_offset;           # offset into the data file

    $size = length(pack("N", 0));
    $i_offset = $size * ($line_number-1);
    seek($index_file, $i_offset, 0) or return;
    read($index_file, $entry, $size);
    $d_offset = unpack("N", $entry);
    seek($data_file, $d_offset, 0);
    return scalar(<$data_file>);
}

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In reply to reading a particular line in a large text file by fadingjava

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