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Old 05-07-2008, 05:28 PM   #1
Registered: Dec 2006
Location: Vancouver, BC
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md5 hash files

I need to understand something...

Say file X has a md5sum of Y. A slight change in X will cause a completely different value for Y, correct?

Therefore when checking md5sums, eyeballing the first and last 3 digits should be sufficient. Am I understanding hash sums correctly?

Last edited by mattydee; 05-07-2008 at 06:33 PM. Reason: spelling
Old 05-07-2008, 05:37 PM   #2
Registered: Feb 2008
Location: Texas
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yup, you got it

although i'd either use an md5sum file and then check it against that or still review the entire string although usually a cursory glance of a few characters as you note is sufficient

$cd /tmp
$echo 1 > example
$md5sum example > example.MD5SUM
$echo 2 > example
$md5sum -c example.MD5SUM
Old 05-07-2008, 06:04 PM   #3
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Experience shows that eyeballing a few characters works most of the time, but it's a terrible habit IMHO. Not only is it much more fool-proof to have the md5sum do the checking for you, it's also simpler (since you only have to look for an "OK"). Hence, I second rayfordj's suggestion that you use a checksum file.
md5sum example.txt > example.txt.md5
md5sum -c example.txt.md5
EDIT: Heh, just noticed rayfordj had already posted an example of the -c option.

Last edited by win32sux; 05-07-2008 at 08:13 PM.
Old 05-07-2008, 06:42 PM   #4
Registered: Dec 2006
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Thanks... I'm lazy


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