The "sha1sum" command:

Compute an SHA1 checksum of all files named on the command-line. If a file is named "-" then take its content from standard input.

Options:

-h|--dereference

If FILE is a symbolic link, compute the hash on the object that the link points to. Normally, the hash is over the name of the object that the link points to.

See also: md5sum, sha3sum