Generating a SHA-256 hash from the Linux command line

I know the string "foobar" generates the SHA-256 hash c3ab8ff13720e8ad9047dd39466b3c8974e592c2fa383d4a3960714caef0c4f2 using

However the command line shell:

hendry@x201 ~$ echo foobar | sha256sum aec070645fe53ee3b3763059376134f058cc337247c978add178b6ccdfb0019f - 

Generates a different hash. What am I missing?

8 Answers

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.

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".

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

/bin/echo -n foobar | sha256sum 

For the sha256 hash in base64, use:

echo -n foo | openssl dgst -binary -sha256 | openssl base64 

Example

echo -n foo | openssl dgst -binary -sha256 | 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.

Use printf instead of echo to avoid adding an extra newline.

printf foobar | sha256sum