command status code的意思|示意

And because every UNIX command returns a status code reflecting success or failure, you can use any command as a conditional — not just the test operators.

而且由于每个UNIX命令都返回一个指示成功或失败的状态代码，因此，您可以使用任何命令作为“条件”——而不仅仅是使用测试操作符。

As you can see from the output of the command, it only returns an error if it gets a status code that doesn't match what is expected.

从命令的输出可以看到，如果获得的状态代码与预期的代码不匹配，将返回一个错误。