Pre-extend a file on Windows

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

To do some alert testing I needed to create a very large file on windows, so I wrote a little perl script to do it. This script works fine on my desktop with ActivePerl 5.8.8. I put it on the servers I need to test with Perl 5.6.1 and it doesn't work at all. Can anyone suggest why?

# Script create_big_file.pl
#
# Generates a file 10gb in size. Use -s to change the size.
#
use Getopt::Std;

my $usage = <<EOT;
Usage: $0 [-h] [-f file] [-s size]
    -h    This help screen.
    -f file    The file to create.
    -s size    Size of the file to create in GB.
    Example: create_big_file.bat -s 26 -f 26gb.dat
EOT

warn($usage), exit(0) if !getopts('hf:s:',\%OPT) or $OPT{'h'};

$filesize = 10000000000;
if ($OPT{'s'}) {
    $filesize = $OPT{'s'} * 1000000000 ;
}
$filename = "oat_bigfile_1.dat";
if ( $OPT{'f'}) {
    $filename = $OPT{'f'};
} 
$size = $filesize -1;

print STDOUT "Creating $filename of $filesize bytes.\n";
open(BIGFILE, "+>", "$filename") || die ("Could not create $filename.\
+n");
binmode BIGFILE;
die("Could not extend $filename to $filesize bytes.\n") unless seek BI
+GFILE, $size, 0;
print BIGFILE "\0";
seek BIGFILE, 0, 0;
close BIGFILE;
[download]

Comment on Pre-extend a file on Windows Download Code

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Re: Pre-extend a file on Windows by BrowserUk (Patriarch) on Jul 13, 2007 at 20:03 UTC
Check the config of your 5.6 perl (`perl -V`) and look for `uselargefiles=define`. If it isn't there, it explains why you cannot seek >2GB, In any case, I'd highly recommend using contig.exe for this. Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error. "Science is about questioning the status quo. Questioning authority". In the absence of evidence, opinion is indistinguishable from prejudice. "Too many [] have been sedated by an oppressive environment of political correctness and risk aversion."	[reply] [d/l] [select]
Re^2: Pre-extend a file on Windows by kenth (Initiate) on Jul 16, 2007 at 12:17 UTC
Thanks for the contig.exe suggestion. That does what I need. I looked at the perl they have installed on the servers and it does not have largefile support compiled in so that explains the problem. Thanks	[reply]
Re: Pre-extend a file on Windows by jwkrahn (Abbot) on Jul 13, 2007 at 19:32 UTC
Can't you just use truncate to create a large file? `$ touch myfile $ ls -l myfile -rw-r--r-- 1 john john 0 2007-07-13 12:30 myfile $ perl -e'truncate "myfile", 200_000_000' $ ls -l myfile -rw-r--r-- 1 john john 200000000 2007-07-13 12:31 myfile` [download]	[reply] [d/l]
Re: Pre-extend a file on Windows by toolic (Bishop) on Jul 13, 2007 at 19:39 UTC
I tried this on my Unix solaris system which has perl 5.6.1, and the cutoff seems to be somewhere between 2G and 3G. I could create a 2G file, but not a 3G file. Could it be an OS limitation, rather than a Perl version issue?	[reply]
Re: Pre-extend a file on Windows by thezip (Vicar) on Jul 13, 2007 at 19:51 UTC
kenth, Did you compile your script in the 5.6 environment? This might have provided an insight into your problem. (Where do I get such stories? It was first implemented in perl 5.6. I go away now...) The three argument form of open did not exist in perl 5.6. You'll need to change the line to read: `open(BIGFILE, "+>$filename") \|\| die ("Could not create $filename.\n");` [download] Also, you'll be using strictures and warnings, right? Where do you want them* to go today?*	[reply] [d/l]
Re: Pre-extend a file on Windows by andreas1234567 (Vicar) on Jul 13, 2007 at 20:03 UTC
What file systems are in use? -- print map{chr}unpack(q{A3}x24,q{074117115116032097110111116104101114032080101114108032104097099107101114})	[reply]