: Broadcast a message to all ttys that a person is logged into.

# System-dependent command (customize for your installation):
MAILER='Mail'		# some systems use 'mailx'

cmd=`basename $0`	# makes diagnostics under csh look better
USAGE="Usage:  $cmd login  Your message here"

# If we have enough args, find out who to talk at.
if [ $# -lt 2 ]
then	echo 1>&2 "$USAGE"; exit 1
else	you=$1; shift
fi

# Send the message to each terminal the specified person is logged into.
# If the person isn't logged in anywhere, mail the message to them.
# This version is non-networked (for local delivery only).

ttys=`who | sed -n '/^'$you' /s/^'$you'  *\(tty[^ ]*\) .*/\1/p'`
if [ -z "$ttys" ]
then	# not logged in
	echo 1>&2 "$cmd: $you not logged in;" \
		"sending your message via mail."
	echo "$@" | $MAILER -s "Hey, $you!" $you
else	# logged in one or more times
	for tty in $ttys
	do
		echo "Hey, $you:  $@" | write $you $tty
	done
fi
.