错误 - 发送：spawn id exp4 未打开

Question

当我运行自动授权用户的脚本时：

expect -c '
 log_user 0
 spawn /usr/bin/sudo su - <username>
 expect "password: "
 sleep 5
 send "password\n"
 interact
'

其结果是：

send: spawn id exp4 not open while executing