exit与wait

[ericming200409]

exit(int status) 的参数是怎么传递给父进程的，我在子进程中exit(2); 为什么在父进程用wait(&eixt_status);为什么得出的结果是：exit_status的值为512

[mymtom]

#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include <unistd.h>

int
main(int argc, char *argv[])
{
        int status;
        pid_t pid;

        pid = fork();

        if (0 == pid) {
                exit(2);
        } else {
                wait(&status);
                printf("status = %d\n", status);
                if (WIFEXITED(status))
                        printf("WEXITSTATUS(status)=%d\n", WEXITSTATUS(status));
        }

        return 0;

[mymtom]

man waitpid
可以查看WIFEXITED, WEXITSTATUS等宏定义的说明。
WIFEXITED(stat_val)
Evaluates to a non-zero value if status was returned for a child process that terminated normally.
WEXITSTATUS(stat_val)
If the value of WIFEXITED(stat_val) is non-zero, this macro evaluates to the low-order 8 bits of the status argument that the child process passed to _exit() or exit(), or the value the child process returned from main().

[yzx714]

wait的值并不是exit的参数，详情请man或者APUE