echo “qwerty http://www.facebook.com” | md5

That will appear in plain text in your terminal history file. And, if you are on a multi-user machine, even non-privileged users will be able to see your command line.

You should never put any password or private key on a command line (any command line, not just in your terminal). Instead, use the unix-standard getpass function or it's equivalent in your language/library of choice.