Puregnome45:

Since you're not chomping your input, you're actually executing two commands "sha1sum $file" and ">data". The second one generates an empty file....

Update: changed "xyz" to "data" to reflect the name used in the OP.

...roboticus

When your only tool is a hammer, all problems look like your thumb.

@files = <STDIN>;

use warnings;
use strict;

for my $file (@ARGV) {
    print "Preforming sha1 on $file\n";
    system( "sha1sum $file >> data" );
}
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Run it like:

code.pl file1 file2 file3
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Fair point, and thanks for remaining me. I meant to mention this in the actual post, but it is showing the output in the console; that is the file is completely empty.

I'll give it like 10 or 15 files to encrypt and it prints sha1's output to the console and still creates the file 'data,' just empty.

I'm not at work to actually test that fix, but I will be sure to first thing in the morning. I'd do it here at home, but I don't have Perl installed, and I'm only going to be working with Perl for another few weeks.

Thanks for the speedy response!

For future reference (as you already have the answer from roboticus), here's a basic debugging technique which can open your eyes to the effects that unexpected data can have on your code: Display what you have, not what you think you have.

Example: Your approach to displaying the information:

    print "Preforming sha1 on $file";
    system( "sha1sum $file > data" );
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Produces:

    Preforming sha1 on test1.dat
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This is fine for human user display, but for programmer debugging display, you've left yourself open to a number of "dirty screen tricks". Instead:

    my $systemCommand = "sha1sum $file > data";
    print "\$systemCommand = [$systemCommand]\n";
    system( $systemCommand );
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Produces:

    $systemCommand = [sha1sum test.dat
     > data]
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Notice how the newline jumps out at you when displayed this way.

I would be remiss to not note that there are two modules folks love to use which might also reveal these problems and more -- Data::Dumpand Data::Dumper. I've seen the effectiveness at these modules helping Monks zero in on a user's issues as if they were painted with red Xs. I highly recommend their use whenever you want to peek at your data in more depth.

Here’s just-a-guess, but I betcha it’s a pretty good guess ...

Your shell-command uses a single greater-than sign ... instead of two.

That is to say, it says shasum $file > data, rather than shasum $file >> data

Therefore, each command is replacing the file named data every time, instead of appending to it, as you probably intend.