Generating a SHA-256 hash from the Linux command line
echo will normally output a newline, which is suppressed with -n. Try this:
echo -n foobar | sha256sum
If you have installed openssl, you can use:
echo -n "foobar" | openssl dgst -sha256
For other algorithms you can replace -sha256 with -md4, -md5, -ripemd160, -sha, -sha1, -sha224, -sha384, -sha512 or -whirlpool.