6.4 b2sum: Print or check BLAKE2 digests

b2sum computes a 512-bit checksum for each specified file. The same usage and options as the md5sum command are supported. See md5sum invocation. In addition b2sum supports the following options.

-l
--length

Change (shorten) the default digest length. This is specified in bits and thus must be a multiple of 8. This option is ignored when --check is specified, as the length is automatically determined when checking.