You can do this cleanly with an ssh ‘control socket’. To talk to an already-running SSH process and get it’s pid, kill it etc. Use the ‘control socket’ (-M for master and -S for socket) as follows:
$ ssh -M -S my-ctrl-socket -fNT -L 50000:localhost:3306 email@example.com $ ssh -S my-ctrl-socket -O check firstname.lastname@example.org Master running (pid=3517) $ ssh -S my-ctrl-socket -O exit email@example.com Exit request sent.
Note that my-ctrl-socket will be an actual file that is created.
I got this info from a very RTFM reply on the OpenSSH mailing list.