Question

我知道，要看到我们上次执行的命令是正确的是shell，我们使用＆＃34; echo $?＆＃34;命令。为什么它返回2作为输出，它意味着什么？

Answer 1

你应该在echo $？之前关注最后一个命令。打开那个命令手册页。你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.

Answer 2

它只显示最后一个命令的错误代码。请检查此链接：Linux System Errors

#define ENOENT           2      /* No such file or directory */

如果＆＃34; echo $？＆＃34;命令返回2？

2 个答案: