rwall - Write to all users over a network
/usr/sbin/rwall -n netgroup...
/usr/sbin/rwall -h hostname -n netgroup
Send the broadcast message to the specified network groups.
Specify the hostname, the name of the host.
The rwall command reads a message from standard input until end-of-file. It
then sends the following message to all users logged in on the specified
host machines, preceded by the line:
Broadcast Message ...
With the -n option, it sends to the specified network groups.
Note, the timeout is fairly short to allow transmission to a large group of
machines (some of which may be down) in a reasonable amount of time. Thus
the message may not get through to a heavily loaded machine.
A remote host only responds if it is running the rwalld daemon, which is
normally started up from inetd(8).
Commands: inetd(8), rwalld(8)