You know the drill by now. :)

Post sample input, sample desired output, code you've tried, and a detailed explanation of the criteria you wish to use in the comparison.

Your problem description leaves me with no understanding of why you would need two temporary files to use in comparing the first fifty characters in two files.

Hi davido,

Actually I stuck with some other work, so could not post whatever I tries so far. Pls find the below code. Actually, the requirement is to find the changed lines in the second file and check all those changes have proper tag. Tag is nothing but the ticket number. The use will make their changes within the first chracters of each line, after that other characters will have comment about the line(contains ticket number also).

use strict;
use warnings;
use Data::Dumper;
use FileIO; # own module to do file operations

my $old_file = shift;
my $new_file = shift;
my $tkt_no = shift;

my @old_version;
my @new_version;
my $error;

#reads the file into array
if (not FileIO::read_file_strip($old_file,\@old_version,\$error)){
        print $error; return;
}
if (not FileIO::read_file_strip($new_file,\@new_version,\$error)){
        print $error; return;
}

my %second_file;

foreach my $oline ( @old_version ){
 my $oshort_line = substr( $oline, 0, 49 );
 $second_file{unpack 'A*', $oshort_line} = $oline;
}

foreach my $nline (@new_version) {
 my $nshort_line = substr( $nline, 0, 49 );
 if( not exists $second_file{unpack 'A*', $nshort_line}){
    my $tmp_str = substr($nline,50,-1);
    if ( defined $tmp_str and $tmp_str ne ""){
       if ( $tmp_str =~ /$tkt_no/){
            print("Tag Valid for $nline\n");
       }
    }else{
       print("Tag not found for $nline\n");
    }
 }
}
[download]

---

All is well. I learn by answering your questions...

G'day vinoth.ree,

After reading this in your OP:

"... read the first 50 characters ..."

these two lines in your code grabbed my attention:

...
my $oshort_line = substr( $oline, 0, 49 );
...
my $nshort_line = substr( $nline, 0, 49 );
...
[download]

I don't know if you thought that's an inclusive range, or something else. See the substr documentation:

"substr EXPR,OFFSET,LENGTH"

To get the first 50 characters from a string, you need OFFSET==0 and LENGTH==50. Here's an example of what you have and one of what you probably want:

$ perl -E 'my $x = "X" x 49 . "Y" x 49; say substr $x, 0, 49'
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
$ perl -E 'my $x = "X" x 49 . "Y" x 49; say substr $x, 0, 50'
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXY
[download]

— Ken

I can't say much more right now because it is not clear to me what you mean by comparing the first 50 characters: do you just need to know if they are equal? Do you need to find the differences? Also, are the files text files? Please provide more details.

sub compare50
  {
  my ($file1, $file2) = @_;
  local $/ = \50; 
  return do {local @ARGV = $file1; <> } eq do {local @ARGV = $file2; <
+> };
  }
[download]

untested...

>  $/ = \50;

Thanks, learned something new about the $INPUT_RECORD_SEPARATOR today. :)

perlvar $/

Setting $/ to a reference to an integer ... will attempt to read records instead of lines ...

Cheers Rolf
_{(addicted to the Perl Programming Language :)
Wikisyntax for the Monastery FootballPerl is like chess, only without the dice}