MacOSX & ssh-agent -l

[joshua stein]

> MacOSX 10.6.x (Snow Leopard) runs { ssh-agent -l }; that's not an
> s/ssh-add/ssh-agent/ typo.  It appears to be an undocumented addition
> (the man-pages were not updated).

look for the #ifdef __APPLE_LAUNCHD__ portions of:

http://opensource.apple.com/source/OpenSSH/OpenSSH-166/openssh/ssh-agent.c

> I *suspect* that it just tells the agent to honour whatever pre-existing
> value of $SSH_AUTH_SOCK it inherits and to try to listen to that.  I
> don't know for sure.

that's correct.  launchd sets up the socket via
/System/Library/LaunchAgents/org.openbsd.ssh-agent.plist and assigns
it to $SSH_AUTH_SOCK.  when ssh tries to read from that socket, it
tells launchd to fire up ssh-agent.