Linux等待进程

在Linux中，可以使用wait()或waitpid()函数让父进程等待子进程的完成。这两个函数都可以阻塞父进程，直到子进程退出或被信号中断。下面是使用waitpid()函数的示例代码：

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/wait.h>

int main()
{ 
    pid_t pid;
    int status;

    pid = fork();

    if (pid == -1)
    {
        printf("error: failed to fork\n");
        exit(1);
    }
    else if (pid == 0) // 子进程
    {
        printf("child process (PID=%d) is running\n", getpid());
        sleep(3); // 子进程休眠3s
        printf("child process (PID=%d) is finished\n", getpid());
        exit(0);
    }
    else // 父进程
    {
        printf("parent process (PID=%d) is waiting for the child (PID=%d) to finish\n", getpid(), pid);
        
        waitpid(pid, &status, 0); // 父进程等待子进程完成
        
        if (WIFEXITED(status))
        {
            printf("parent process received child exit status: %d\n", WEXITSTATUS(status));
        }
        
        printf("parent process is exiting\n");
    }

    return 0;
}