4.2BSD/usr/man/man1/write.1

.TH WRITE 1  "18 January 1983"
.SH NAME
write \- write to another user
.SH SYNOPSIS
.B write
user [ ttyname ]
.SH DESCRIPTION
.I Write
copies lines from your terminal to that of
another user.
When first called,
it sends the message
.PP
     Message from yoursystem!yourname yourttyname...
.PP
The recipient of the message should write back at this point.
Communication continues until an end of file is
read from the terminal or an interrupt is sent.
At that point
.I write
writes `EOT' on the other terminal and exits.
.PP
If you want to write to a user who is logged in more than once,
the
.I ttyname
argument may be used to indicate the
appropriate terminal name.
.PP
Permission to write may be denied or granted by use of the
.I mesg
command.
At the outset writing is allowed.
Certain commands, in particular
.I nroff
and
.IR  pr (1)
disallow
messages in order to prevent messy output.
.PP
If the character `!' is found at the beginning of a line,
.I write
calls the shell
to execute the rest of the
line as a command.
.PP
The following protocol is suggested for using
.IR write :
when you first write to another user, wait for him to
write back before starting to send.
Each party should end each message with a distinctive
signal\(em\fB(o)\fR
for `over' is conventional\(emthat the other may reply.
.B (oo)
for `over and out' is suggested when conversation
is about to be terminated.
.SH FILES
/etc/utmp	to find user
.br
/bin/sh		to execute `!'
.SH "SEE ALSO"
mesg(1), who(1), mail(1)