为什么wait()将状态设置为255，而不是分叉进程的-1退出状态? [英] Why does wait() set status to 255 instead of the -1 exit status of the forked process?

问题描述

我正在尝试从子进程中返回一个整数值.

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

但是，如果我使用 exit(1)，则会得到 256 作为 wait()的输出.使用 exit(-1)给出 65280 .

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

有没有办法获取子进程发送的实际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);

使用 exit(-1)(这是我真正想要的)，我得到255作为 WEXITSTATUS(status)的输出.它应该是未签名的吗?

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"man waitpid"?

Have you tried "man waitpid"?

从waitpid()调用返回的值是退出值的编码.有一组宏将提供原始的退出值.或者，如果您不关心可移植性，则可以尝试将值右移8位.

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.

您的代码的可移植版本为:

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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