If you wish to talk to someone on you own machine, then person is just the person's login name. If you wish to talk to a user on another host, then person is of the form :
host!user
or
host.user
or
host:user
or
user@host
though user@host is perhaps preferred.
If you want to talk to a user who is logged in more than once, the ttyname argument may be used to indicate the appropriate terminal name.
When first called, it sends the message
Message from TalkDaemon@his_machine...
talk: connection requested by your_name@your_machine.
talk: respond with: talk your_name@your_machine
to the user you wish to talk to. At this point, the recipient of the message should reply by typing
It doesn't matter from which machine the recipient replies, as long as his login-name is the same. Once communication is established, the two parties may type simultaneously, with their output appearing in separate windows. Typing control L will cause the screen to be reprinted, while your erase, kill, and word kill characters will work in talk as normal. To exit, just type your interrupt character; talk then moves the cursor to the bottom of the screen and restores the terminal.
Permission to talk may be denied or granted by use of the mesg command. At the outset talking is allowed. Certain commands, in particular nroff and pr(1) disallow messages in order to prevent messy output.
/etc/utmp to find the recipient's tty