Write (Unix)

In Unix and Unix-like operating systems, write is a utility used to send messages to another user by writing a message directly to another user's TTY.
History.
The write command was included in the First Edition of the Research Unix operating system.
Sample usage.
The syntax for the write command is:
$ write user [tty]
message
The write session is terminated by sending EOF, which can be done by pressing Ctrl+D. The "tty" argument is only necessary when a user is logged into more than one terminal.
A conversation initiated between two users on the same machine:
$ write root pts/7
test
Will show up to the user on that console as:
Message from root@wiki on pts/8 at 11:19 ...
test