How do I pass a password to hdiutil attach? How do I pass a password to hdiutil attach?

I have an encrypted sparsebundle  (test.sparsebundle) and it's password is "test", with no quotes.

I'd like to automate opening that file.

I have tried 

echo "test" | hdiutil attach -stdinpass test.sparsebundle


and

echo test | hdiutil attach -stdinpass test.sparsebundle


But it returns

hdiutil: attach failed - Authentication error
Ah! A little more digging, and careful reading of the man page. I need a null terminated string.

So 

printf '%s\0' 'test' | hdiutil attach test.sparsebundle -stdinpass


works.