The issue stems from a problem with a few boxes I assist administering. When copying files over NFS to one host or via SMB, both originating from Unix (Samba) or NT (Exceed) to the other, occasionally the destination file ends up with the correct file size, but has white space replacing large chunks of the file. 95% of the various and mixed boxes exhibit no issues.

The customer, and I for sanity, wants something akin to a CRC or checksum involved in the copy process. See my sample below.

THX
Dex\

#!/usr/bin/perl -w
# -*-Perl-*-

use strict;
use FileHandle;
use Digest::MD5;

my $sourceFile = $ARGV[0];
my $destFile   = $ARGV[1];
my $inFile     = new FileHandle;
my $outFile    = new FileHandle;
my $inMD5      = Digest::MD5->new;
my $outMD5     = Digest::MD5->new;
my ( 
    $fileLength,
    $fileBuffer,
    $fileOffset
   );

$inFile->open ( "<$sourceFile" )
  or die "Could not open $sourceFile:$!\n";
$inMD5->addfile ( $inFile );

$outFile->open ( ">$destFile" )
  or die "Could not open $destFile:$!\n";

print $inMD5->md5_base64 , "\n";

# borrowed from "Programming Perl"

my $blockSize = ( stat $inFile )[11] || 16384;
while ( $fileLength  = sysread $inFile, $fileBuffer, $blockSize ) {
    if ( !defined $fileLength ) {
 next
   if $! =~ /^Interrupted/;
 die "System read error: $!\n";
    }
    my $fileOffset = 0;
    while ( $fileLength ) {
 my $written = syswrite $outFile, $fileBuffer, $fileLength, $fileOffse
+t;
 die "System write error: $!\n"
   unless defined $written;
 $fileLength -= $written;
 $fileOffset += $written;
    };
}

$outMD5->addfile ( $outFile );
print $outMD5->md5_base64 , "\n";

$inFile->close;
$outFile->close;
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2001-03-14 Edit by Corion: Moved the explanation of the problem up from a reply into the root node.