[linux] Generating a SHA-256 hash from the Linux command line

I know the string "foobar" generates the SHA-256 hash c3ab8ff13720e8ad9047dd39466b3c8974e592c2fa383d4a3960714caef0c4f2 using http://hash.online-convert.com/sha256-generator

However the command line shell:

hendry@x201 ~$ echo foobar | sha256sum
aec070645fe53ee3b3763059376134f058cc337247c978add178b6ccdfb0019f  -

Generates a different hash. What am I missing?

echo produces a trailing newline character which is hashed too. Try:

/bin/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.

For the sha256 hash in base64, use:

echo -n foo | openssl dgst -binary -sha1 | openssl base64

Example

echo -n foo | openssl dgst -binary -sha1 | openssl base64
C+7Hteo/D9vJXQ3UfzxbwnXaijM=

I believe that echo outputs a trailing newline. Try using -n as a parameter to echo to skip the newline.

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".

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