为什么等待（）将状态设置为256，而不是派生进程的-1退出状态？ [英] Why does wait() set status to 256 instead of the -1 exit status of the forked process?

问题描述

我想从一个子进程返回一个整数值。

I'm trying to return an integer value from a child process.

不过，如果我使用退出（1）我得到的 256 作为输出。 退出（-1）给 65280

However, if I use exit(1) i get 256 as the output. exit(-1) gives 65280.

有没有一种方法，我可以得到我从子进程发送实际的int值？

Is there a way I can get the actual int value that I send from the child process?

if(!(pid=fork()))
{
    exit(1);
}
waitpid(pid,&status,0);
printf("%d",status);

编辑：是退出（-1）（这是我真正想要的）我得到255的输出WEXITSTATUS（状态）。难道应该是无符号的？

Using exit(-1) (which is what I actually want) I am getting 255 as the output for WEXITSTATUS(status). Is it supposed to be unsigned?

推荐答案

您是否尝试过人waitpid函数？

Have you tried "man waitpid"?

从waitpid函数（）调用返回的值是退出值的编码。有一组宏，将提供原出口价值。或者你可以尝试用权移入8位的值，如果你不关心可移植性。

The value returned from the waitpid() call is an encoding of the exit value. There are a set of macros that will provide the original exit value. Or you can try right shifting the value by 8 bits, if you don't care about portability.

您code的移植版将是：

The portable version of your code would be:

if(!(pid=fork()))
{
    exit(1);
}
waitpid(pid,&status,0);
if (WIFEXITED(status)) {
    printf("%d", WEXITSTATUS(status));
}

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