How to create md5 hash in bash in Mac OS X

How can you create an md5 hash for a string on a mac using bash? md5sum does not exist in my environment. I did a man for md5 but I'm confused about what that really does.

md5 "string"

does not return a hash.

This should work -

[jaypal:~/Temp] echo "this will be encrypted" | md5
72caf9daf910b5ef86796f74c20b7e0b

or if you prefer here string notation then -

[jaypal:~/Temp] md5 <<< 'this will be encrypted'
72caf9daf910b5ef86796f74c20b7e0b

UPDATE:

Per the man page, you can play around with any of the following options

-s string
        Print a checksum of the given string.

-p      Echo stdin to stdout and append the checksum to stdout.

-q      Quiet mode - only the checksum is printed out.  Overrides the -r option.


[jaypal:~/Temp] md5 -s 'this will be encrypted'
MD5 ("this will be encrypted") = 502810f799de274ff7840a1549cd028a

[jaypal:~/Temp] md5 -qs 'this will be encrypted'
502810f799de274ff7840a1549cd028a

Note: MD5 always produces the same hash. The reason you find the output different from the example given above is due to a point that has been made in the comments. The first two examples use the trailing newline character to produce the hash. To avoid that, you can use:

[jaypal:~/Temp] echo -n "this will be encrypted" | md5
502810f799de274ff7840a1549cd028a

For example, if you use echo -n "string" | md5 (note the -n option), you get b45cffe084dd3d20d928bee85e7b0f21. But, if you use echo "string" | md5, you get b80fa55b1234f1935cea559d9efbc39a.

Or, verify it with the shell:

➜  [jaypal:~/Temp] [ $(echo "HOLA" | md5) = $(echo "HOLA" -n | md5) ]; echo "$?"
1
# 1 -> False. Hence, the result from echoing "HOLA" toggling the -n flag
# outputs different md5 checksums.

To achieve what you asked:

md5 -s string

outputs: MD5 ("string") = b45cffe084dd3d20d928bee85e7b0f21

OSX uses md5 but most unices use md5sum

Here is a section of rvm's rvmrc validation code which finds the correct md5 binary and wraps it.

__rvm_md5_for()
{
  if builtin command -v md5 > /dev/null; then
    echo "$1" | md5
  elif builtin command -v md5sum > /dev/null ; then
    echo "$1" | md5sum | awk '{print $1}'
  else
    rvm_error "Neither md5 nor md5sum were found in the PATH"
    return 1
  fi

  return 0
}

( Code from https://github.com/wayneeseguin/rvm/blob/master/scripts/functions/rvmrc )

The correct way of doing that would be echo -n string | md5 instead of echo "string" | md5. (I am using zsh)

Convert the md5 hash given by echo -n string | md5 you will get back string.

md5 -s string also works which is already pointed out here.

λ [~] → echo "string" | md5
b80fa55b1234f1935cea559d9efbc39a

λ [~] → echo -n string | md5
b45cffe084dd3d20d928bee85e7b0f21

λ [~] → md5 -s string
MD5 ("string") = b45cffe084dd3d20d928bee85e7b0f21

All the other answers are valid. I would like to also propose openssl as well:

➜ echo 'this will be hashed' | openssl md5
55be2dc2df2c1cc7bad72a0ecb338841

which is equivalent to the following

➜ echo 'this will be hashed' | openssl dgst -md5
# or
➜ openssl md5 <<< 'this will be hashed'
# or
➜ echo 'this will be hashed' | md5

From the command line:

md5 <<< "String to hash"
8a0a39505c5753ff64a0377ab0265509

You may want to use some randomness here, otherwise the password will always be the same. This should work:

dd if=/dev/random count=20|md5