For -opt, the value of arg is used as the replacement value only if a value has been defined for all of the listed variables.

对于- opt，只有为列出的所有变量定义一个值时，才能将arg的值用作替换值。

youdao

For -opt, the value of arg is used as the replacement value only if a value has been defined for all of the listed variables.

对于- opt，只有为列出的所有变量定义一个值时，才能将arg的值用作替换值。

youdao