Re: File integrity checker

Would like to check the integrity of the file before attempting uncompression or extraction.

There's not really any way to do this. Zip and gzip store checksums of the uncompressed contents; the -t options actually uncompress the file, calculate the checksum, and throw away the contents. You could do the same thing in your program, or you could uncompress to a tempfile and delete it if the checksum comes out bad.

Edit: There's a section about integrity checking in the Archive::Zip::FAQ.

Comment on Re: File integrity checker

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Re^2: File integrity checker by roperl (Beadle) on Aug 24, 2017 at 16:49 UTC
Thanks, yes the integrity check section in Archive::Zip::FAQ seems to be exactly what I need for zip files I'm already gunzipping the gz files to a temp file name. So how do would I get the the checksum of the uncompressed file and what do I compare it to?	[reply]
Re^3: File integrity checker by pryrt (Abbot) on Aug 24, 2017 at 17:06 UTC
The "checksum" is the same as the "CRC" referenced in the FAQ. The FAQ mentions example code in the CPAN distribution that shows how to calculate the CRC.	[reply]
Re^3: File integrity checker by Anonymous Monk on Aug 24, 2017 at 17:14 UTC
IO::Uncompress::Gunzip will check the sum for you if you set the Strict option: `gunzip 'file.gz', 'file.out', Strict=>1 or die $GunzipError;` [download]	[reply] [d/l]
Re^4: File integrity checker by no_slogan (Deacon) on Aug 24, 2017 at 17:37 UTC
BTW, if you want to test your error-checking code, you can break the stored checksum like this: `open my $F, '+<', 'file.gz' or die $!; seek $F, -8, 2; my $c = getc($F); seek $F, -8, 2; print $F chr(ord($c) ^ 1);` [download] Running this a second time will fix the .gz file.	[reply] [d/l]
Re^5: File integrity checker by roperl (Beadle) on Aug 24, 2017 at 21:05 UTC
Re^4: File integrity checker by roperl (Beadle) on Aug 24, 2017 at 18:42 UTC
Thanks that is helpful So how is `my $retval = gunzip 'file.gz' => 'file.out', Strict=>1 or $GunzipError +;` [download] different than `my $retval = gunzip 'file.gz', 'file.out', Strict=>1 or $GunzipError;` [download]	[reply] [d/l] [select]
Re^5: File integrity checker by no_slogan (Deacon) on Aug 24, 2017 at 18:48 UTC


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