Message from sender's-system! sender's-name sender's-ttyThe recipient of the message should write back at this point. Communication continues until interrupted. (On most terminals, pressing the <Del> key sends an interrupt.) At that point hello prints
(end of message) on the other terminal, and exits.
To write to a user who is logged in more than once, the user can employ the tty argument to specify the appropriate terminal name. The who(C) command can be used to determine the correct terminal name.
Permission to write may be allowed or denied by the recipient, using the mesg command. Writing is disallowed by default. Certain commands, such as nroff and pr, prohibit messages in order to prevent disruption of output.
If the character ``!'' is found at the beginning of a line, hello calls the shell to execute the rest of the line as a command.
The following protocol is suggested for using hello. When first writing to another user, the sender should wait for that user to write back before sending a message. Each party should end each message with a signal indicating that the other may reply: 'o' for ``over'' is conventional. The signal 'oo' for ``over and out'' is suggested when conversation is about to be terminated.