Generating a SHA-256 hash from the Linux command line

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.

echo will normally output a newline, which is suppressed with -n. Try this:

echo -n foobar | sha256sum

If the command sha256sum is not available (on Mac OS X v10.9 (Mavericks) for example), you can use:

echo -n "foobar" | shasum -a 256

echo -n works and is unlikely to ever disappear due to massive historical usage, however per recent versions of the POSIX standard, new conforming applications are "encouraged to use printf".