Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:


Script 1, stand alone script passing the name of a zip file:
use Digest::SHA1;
$sha1 = Digest::SHA1->new;


$fhIN = $ARGV[0];
open(IN,$fhIN) || die "\ncan open file for input";
binmode IN;
$sha1->addfile(IN);
$digest = $sha1->hexdigest;


print "$digest\n";

[download]
Output:50bd187a208112091b035c62209baf9742c243bd
script 2, part of a CGI, passing the path to the same file as above:
sub generateDigest{
my ($file) = @_;
my $sha1 = Digest::SHA1->new;
open(FILE, $file) || die;
binmode FILE;
$sha1->addfile(*FILE);
close(FILE);
my $digest = $sha1->hexdigest;
warn "$digest";
return $digest;
}

[download]
Output: 7ba6487fefcc4467b21deccac79b38d7d3b69bf2
Why the difference?

Replies are listed 'Best First'.
Re: Digest::Sha1 differences
by moritz (Cardinal) on May 19, 2010 at 13:25 UTC
    Read the documentation again: 
    $sha1->addfile(*FILE);

    (Emphasis by me). In one of the cases you forgot the *

    Perl 6 - links to (nearly) everything that is Perl 6.
[reply]
[d/l]
      In one of the cases you forgot the *

      Interestingly, I don't get any difference in SHA1 (with or without the * — though the latter doesn't work with strictures of course, i.e. it gives Bareword "IN" not allowed while "strict subs" in use). 

      #!/usr/bin/perl -l

#use strict;
use warnings;
use Digest::SHA1;

my $fname = $ARGV[0];
my $sha1;

open(IN, $fname) || die "can't open '$fname' for input: $!";
binmode IN;
$sha1 = Digest::SHA1->new;
$sha1->addfile(IN);
print $sha1->hexdigest;

open(IN, $fname) || die "can't open '$fname' for input: $!";
binmode IN;
$sha1 = Digest::SHA1->new;
$sha1->addfile(*IN);
print $sha1->hexdigest;

open(my $fhIN, $fname) || die "can't open '$fname' for input: $!";
binmode $fhIN;
$sha1 = Digest::SHA1->new;
$sha1->addfile($fhIN);
print $sha1->hexdigest;

system 'sha1sum', $fname;

      [download]

      Output for a file "foo" containing "bar\n": 

      $ ./840698.pl foo
e242ed3bffccdf271b7fbaf34ed72d089537b42f
e242ed3bffccdf271b7fbaf34ed72d089537b42f
e242ed3bffccdf271b7fbaf34ed72d089537b42f
e242ed3bffccdf271b7fbaf34ed72d089537b42f  foo

      [download]

      Anyhow, to avoid the confusion, the OP could've used a lexical file handle, as shown in the third variant above.

[reply]
[d/l]
[select]
        So you see no difference? Weird! I'm using a zip file of 60mb in my example. I'm on perl 5.8 on a sun solaris server. COuld there be some sort of problem relating to the size of the source file I want to make a digest of? Thanks
[reply]
      thank you, can you tell me what the first example is creating a digest of? the file name?
[reply]
        If it reads from the handle as long as it can, it hashes the empty string.

        But you'd have to look into the source to find out for sure.

[reply]

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