comparison of 2 text files

[tilu]

I have two text files. How do I compare using perl?

-Tilu

[miller]

That depends. In what way do you want to compare them.

- Miller

[sujay1983]

Hi,

If you are running your script in a unix environment, then better use the diff command.

`diff file1 file2 > output.txt`

[tilu]

That depends. In what way do you want to compare them.

- Miller

I want to write a perl script to compare line by line the two text files.

[Freedolen]

You can use any pre-defined modules such as Text::Diff or you can modify/use the following coding

use strict;
use warnings;
 
my $firstfile = 'test1.txt';
my $secondfile = 'test2.txt';
 
open(F1, $firstfile) or die "Unable to open $firstfile $!\n";
open(F2, $secondfile) or die "Unable to open $secondfile $!\n";
 
my @firstfile = <F1>;
my @secondfile = <F2>;
 
if (@firstfile != @secondfile) {
    print (@firstfile > @secondfile)
        ? "File $firstfile has more lines than $secondfile\n"
        : "File $secondfile has more lines than $firstfile\n";
} else {
    for my $i (0..$#firstfile) {
        if ($firstfile[$i] ne $secondfile[$i]) {
            print "Difference Found in Line-" . ($i+1) . ":\n$firstfile: $firstfile[$i]\n$secondfile: $secondfile[$i]\n";
        }
    }
}
 
close (F1);
close (F2);
 

[KevinADC]

Hi,

If you are running your script in a unix environment, then better use the diff command.

`diff file1 file2 > output.txt`

Why is that suggestion "better" than using perl?

[numberwhun]

Why is that suggestion "better" than using perl?

I would say its not "better" than using Perl, just much quicker as you wouldn't be re-inventing the wheel. Granted, I am one that is all for re-inventing the wheel in order to learn, but if you are needing a quick, right now fix, then I would certainly use the system diff utility.

jlk

[tilu]

Thanks.. Its useful.

--tilu

You can use any pre-defined modules such as Text::Diff or you can modify/use the following coding

use strict;
use warnings;
 
my $firstfile = 'test1.txt';
my $secondfile = 'test2.txt';
 
open(F1, $firstfile) or die "Unable to open $firstfile $!\n";
open(F2, $secondfile) or die "Unable to open $secondfile $!\n";
 
my @firstfile = <F1>;
my @secondfile = <F2>;
 
if(scalar(@firstfile) == scalar(@secondfile))
{
    for(my $i = 0; $i<=$#firstfile; $i++)
    {
        if($firstfile[$i] eq $secondfile[$i])
        {
        }
        else
        {
            print "Difference Found in Line-".($i+1).":\n$firstfile: $firstfile[$i]\n$secondfile: $secondfile[$i]\n";
        }
    }
}
else
{
    (scalar(@firstfile)>scalar(@secondfile))?print "File $firstfile has more lines than $secondfile\n":print "File $secondfile has more lines than $firstfile\n";
}
close (F1);
close (F2);
 
 
 

[KevinADC]

I would say its not "better" than using Perl, just much quicker as you wouldn't be re-inventing the wheel. Granted, I am one that is all for re-inventing the wheel in order to learn, but if you are needing a quick, right now fix, then I would certainly use the system diff utility.

jlk

How is it quicker? That would only be true if a person already knows the shell commands and is using an OS that supports it. Nix users seem to think everyone uses nix.

[miller]

I want to write a perl script to compare line by line the two text files.

When I asked in what way you wanted to compare them, I suppose I should have been more specific. Generally when comparing files, you're either testing for equality or for difference.

For equality, there is a cpan module called File::Compare that I believe would do the job.

For difference, the Text::Diff module that Freedolen mentioned would almost certainly do the trick.

- Miller

[AdrianH]

How is it quicker? That would only be true if a person already knows the shell commands and is using an OS that supports it. Nix users seem to think everyone uses nix.

Nix users? ;) I've usually used a wildcard in front of that :D though it doesn't cover Linux quite right.

Sorry, but though these utilities came from an OS that is closer to the primordial ooze of computing OSs, there are plenty of gnu ports to most all if not all other OSs platforms.

See MinGW or Cygwin for a more packaged implementation, or look for individual binaries.

I've also found that once you understand the nix utils, you will find that most of your scripting needs are done for you, so it may be slightly longer short term, but long term you're set.


Adrian