How do I send a notification to all active shells, like shutdown does?

Question

You know, I was just there, doing my things, when suddenly a terrible Broadcast message appeared!

fiatjaf@mises ~> sl
fiatjaf@mises ~> ls dotfiles/
urxvt
vim/
vimrc
fiatjaf@mises ~> cowsay good morning
 ______________
< good morning >
 --------------
        \   ^__^
         \  (oo)\_______
            (__)\       )\/\
                ||----w |
                ||     ||
fiatjaf@mises ~> 
fiatjaf@mises ~> 
Broadcast message from root@mises
    (/dev/pts/3) at 11:12 ...

The system is going down for maintenance NOW!

How can trigger a message like this from my own programs?

score 8 · Accepted Answer · edited Apr 13 '17 at 12:37

8

man wall will give you what you need.

You execute wall with either a filename, or you pipe content to it.

For example, either,

wall file.name to broadcast the content of the file file.name or

echo "Dive\!" | wall to send the message Dive!

Update: As Stephen points out in this answer, later versions of wall can send messages by simply typing,

wall message text here

and in fact, there are additional restrictions on non-root users sending the contents of files by specifying only the file name.

edited Apr 13 '17 at 12:37

Community

1

answered Apr 20 '16 at 14:22

EightBitTony

21,373

It works! Thank you. But why it doesn't work on urxvt, only on gnome-terminal? – fiatjaf Apr 20 '16 at 14:26
See http://unix.stackexchange.com/questions/150697/broadcast-messages-dont-appear-on-gnome-terminal-but-appear-on-xterm – fiatjaf Apr 20 '16 at 14:32
2

what's the output of mesg? "mesg n" would inhibit a wall (in Linux, anyway) – Jeff Schaller Apr 20 '16 at 14:37
1

I think it's actually a known issue with urxvt, a quick search shows several queries asking why wall's don't arrive. – EightBitTony Apr 20 '16 at 14:39

Stephen Kitt · Answer 2 · 2016-04-20T14:35:31.540

4

You simply use wall; running it as root will ensure every terminal displays the message.

wall Your attention please\!

Older versions of wall only accept a file name on their command-line, or a message piped in:

echo Your attention please\! | wall

edited Apr 20 '16 at 14:35

answered Apr 20 '16 at 14:22

Stephen Kitt

434,908

Thank you, but it isn't working like this, it is asking for a file. – fiatjaf Apr 20 '16 at 14:25
1

wall displays either the contents of a file (when run as wall file) or it's standard input (so run as echo hello | wall). wall <text> doesn't work on Linux. – EightBitTony Apr 20 '16 at 14:28
1

Yes it does, perhaps only in recent versions bsdutils or util-linux though. – Stephen Kitt Apr 20 '16 at 14:33

How do I send a notification to all active shells, like shutdown does?

2 Answers2