linux - 如果 "echo $?"命令返回 2 怎么办？

Question

我知道，要查看我们最后执行的命令是否正确是 shell，我们使用“echo $?”命令。为什么它返回 2 作为输出，这意味着什么？

Answer 1

您应该关注 echo $? 之前的最后一个命令。打开该命令手册页。您可以找到退出代码的含义。

例如；

man grep;
...
EXIT STATUS
The exit status is 0 if selected lines are found, and 1 if not found.  
If an error occurred the exit status is 2.  
(Note: POSIX error handling code should check for '2' or greater.)
....

或

man ls;

   Exit status:
       0      if OK,

       1      if minor problems (e.g., cannot access subdirectory),

       2      if serious trouble (e.g., cannot access command-line argument).

或

man diff

 Exit status is 0 if inputs are
       the same, 1 if different, 2 if trouble.