Generating a SHA-256 hash from the Linux command line

279
votes

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?

7
linuxshellsha256
sha256sum < foobar. No need for cat, echo, printf, ... See also Useless use of cat? - koppor
@koppor < foobar is not the same as echo foobar |. The equivalent for echo foobar | would be sha256sum <<< foobar but that does add a newline to foobar just like echo. - mvds

7 Answers

435
votes

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

echo -n foobar | sha256sum
111
votes

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.

48
votes

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

31
votes

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".

9
votes

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

/bin/echo -n foobar | sha256sum
7
votes

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

2
votes

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=