Other communication facilities
Electronic mail is useful for sending messages, but not for
holding a 'conversation', nor for sending urgent messages (since
not all users will read mail very frequently). Two utilities are
provided in UNIX to enable 'real-time' communication between logged
in users. The first is write: suppose user
sam is logged on, and you wish to send Sam a (short)
message; use write sam followed by the lines of the
message then ctrl-D.
$ write sam
Hi Sam.
It's coffee time
The message will be sent across line-by-line. Your message will
appear on Sam's screen, preceded by a line telling sam
who's sending the message:
Message from chris@box on ttyp9 at 14:42 ...
Hi Sam.
It's coffee time
If sam was logged on at several terminals at once
(which is possible if Sam has multiple windows on a graphics
display), you could specify the terminal the message should appear
on, so:
$ write sam ttyp7
Sam can reply to you with the command write chris.
Whatever sam is doing, the lines you type will appear
on Sam's screen. It could be that the recipient of your message
does not want this to happen (perhaps he or she is doing a
complicated operation and doesn't wish to be disturbed). They can
prevent messages being displayed by means of mesg. To
deny other users permission to write messages to your screen, type
mesg n. To reinstate permission, mesg y
will reverse the effect of mesg n. If you try to
write to a user who has denied you permission, you
will simply get an error message. The second communications
mechanism is talk. Rather than sending lines of
messages, talk is the nearest you will come to
actually talking to another user. It sends messages
character-by-character as you type them in, and will work over
networks. To run talk, the syntax is just as for
write. After you have typed talk sam, a
message will appear on Sam's terminal:
Message from chris@box
talk: connection requested by chris@box
talk: respond with: talk chris@box
When sam types talk chris@box (or
whatever address talk specifies) both your screen and
Sam's will be cleared, and divided into separate regions, one for
each of you. When you press a key, it will appear in 'your' part of
the screen, when Sam presses one the corresponding character will
appear in 'their' part. You can use the DELETE key if you
press a key by mistake. Your conversation will be terminated when
either of you presses ctrl-C. Standard input and standard
output are not the mechanisms employed by talk. Find a
friend who is also logged in and experiment with write
and talk.
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