write(1) - Unix First Edition Manual Page
11/3/71WRITE (I)

NAME write -- write to another user
SYNOPSIS write user
DESCRIPTION write copies lines from your typewriter to that of anotheruser. When first called, write sends the message

message from yourname... The recipient of the message should write back at thispoint. Communication continues until an end of file is read from the typewriter or an interrupt is sent. At that pointwrite writes "EOT" on the other terminal.

Permission to write may be denied or granted by use of themesg command. At the outset writing is allowed. Certain commands, in particular roff and pr, disallow messages inorder to prevent messy output.

If the character "!" is found at the beginning of a line,write calls the mini--shell msh to execute the rest of the line as a command. The following protocol is suggested for using write: Whenyou first write to another user, wait for him to write back before starting to send. Each party should end each messagewith a distinctive signal ("(o)" for "over is conventional)that the other may reply. "(oo)" (for over andout") is suggested when conversation is about to be terminated.
FILES /tmp/utmp is used to discover the target user's typewriterchannel and the sending users s name. msh is used to

execute commands.
DIAGNOSTICS "user not logged in"; "permission denied"
OWNER dmr, ken

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