$ sha1sum file.iso
or
$ sha1sum file.txt
prints the checksum/SHA1 fingerprint of the file in question.
This can be used for checking the data integrity or corruption.
This technology is also used in a different way for detecting intrusion in
tripwire.
Normally you don't use it with any switch.
You have to execute the same command on two different machines and
verify the output.
It is usually enough to look at the first 4 and the last 4 characters
of the output.
Since a very minor change in input will result in a completely
different output, this
method is invaluable.
Look at it as a nice accompaniment to diff to detect file changes.
-Girish
--
Gayatri Hitech
web: http://gayatri-hitech.com
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