A question mark indicates an invalid option, in which case the character triggering it is stored in the variable optopt.
问号表示无效选项，在这种情况下，触发它的字符存储在变量optopt中。
A question mark indicates an invalid option, in which case the character triggering it is stored in the variable optopt.
问号表示无效选项，在这种情况下，触发它的字符存储在变量optopt中。
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