sha1sum computes a 160-bit checksum for each specified file. The usage and options of this command are precisely the same as for md5sum. See md5sum invocation.
Note: The SHA-1 digest is more secure than MD5, and no collisions of it are known (different files having the same fingerprint). However, it is known that they can be produced with considerable, but not unreasonable, resources. For this reason, it is generally considered that SHA-1 should be gradually phased out in favor of the more secure SHA-2 hash algorithms. See sha2 utilities.