比如d命令，输入.d的话还能纠错，输入 .!d 就会导致报错进入busy了 报错信息：

.!d
<.shell waiting 1 second(s) for process>
'd' ?????????��?????��?????????????????????�� 
?��?��???��?????? 
.shell: Process exited
Press ENTER to continue
<.shell waiting 1 second(s) for process>
<.shell process may need input>