6.6 sha1sum: Print or check SHA-1 digests

sha1sum computes a 160-bit checksum for each specified file.

Note: The SHA-1 digest is more reliable than a simple CRC (provided by the cksum command) for detecting accidental file corruption, as the chances of accidentally having two files with identical SHA-1 are vanishingly small. However, it should not be considered secure against malicious tampering: although finding a file with a given SHA-1 fingerprint is considered infeasible at the moment, it is known how to modify certain files, including digital certificates, so that they appear valid when signed with an SHA-1 digest. For more secure hashes, consider using SHA-2, or the newer b2sum command. See sha2 utilities: Print or check SHA-2 digests. See b2sum: Print or check BLAKE2 digests.

If a file is specified as ‘-’ or if no files are given sha1sum computes the checksum for the standard input. sha1sum can also determine whether a file and checksum are consistent. Synopsis:

sha1sum [option]… [file]…

sha1sum uses the ‘Untagged output format’ for each specified file, as described at cksum output modes.

The program accepts cksum common options. Also see Common options.