set timeout 60

spawn socat unix-connect:foo.sock -
send "\r\n"
expect "login:" {  send "root\r\n" }
expect "/ #"
set FINISHED 0
set EXIT "1" 
while { $FINISHED < 5 } {
  send "ip address show dev ppp0 | grep ppp0\r\n"
  
  expect {
    "192.168.100.1" { set FINISHED 10; set EXIT 0; }
    "can't find device" { send_user "waiting ..." ; send "\r\n"; sleep 3 }
  }
  set FINISHED [ expr $FINISHED + 1 ]
}

exit $EXIT