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.
[1] The write command was included in the First Edition of the Research Unix operating system.
[2] A similar command appeared in Compatible Time-Sharing System.
[3] The syntax for the write command is: 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.