sha1sum

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sha1sum is a computer program which calculates and verifies SHA1 hashes. It is commonly used to verify the integrity of files. It is installed by default in most Unix, GNU/Linux and BSD operating systems. Versions for Microsoft Windows do exist (see external links).

Note that some cryptographical weaknesses have been found in SHA1, and in situations where security is important it may be wise to use a better algorithm. However, sha1sum is still very much usable for general-purpose file checksumming, and better than MD5 or a CRC.

[edit] Usage

To calculate the SHA1 hash of a file, simply give the filename as an argument to sha1sum.

$ sha1sum somefile
da39a3ee5e6b4b0d3255bfef95601890afd80709  somefile

The output of sha1sum can be saved into a text file and used to verify the integrity of a file. If the output above is stored in the file somefile.sha1, the following command will compare the SHA1 hash of somefile with the hash stored in somefile.sha1.

$ sha1sum -c somefile.sha1
somefile: OK

The sha1sum command can also be used in an interactive mode to calculate the SHA1 hash of any arbitrary string of characters. After typing the sha1sum command without any arguments, type the string of characters in the terminal. End the string with an End-of-file character. The SHA1 hash will be displayed on the terminal next to the input string. For example:

$ sha1sum
somestring CTRL+D CTRL+D

will result in the following output.

$ sha1sum
somestringda63fb69aeb03c776bd23e91e2c1cb3df30135d3  -

[edit] See also

[edit] External links