0707 父子进程之间传递文件描述符

/*************************************************************************
    > File Name: pass_fd.c
    > Author:Monica
    > Mail:liling222@126.com 
    > Created Time: Mon 07 Jul 2014 09:52:49 PM CST
 ************************************************************************/

#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <strings.h>
#include <stdlib.h>
#include <unistd.h>
#include <signal.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <string.h>

void my_handler(int signum)
{
    wait(NULL);
    exit(0);
}
void send_n(int fd_socket, int fd_to_send);
void recv_n(int fd_socket, int* fd_to_recv);

int main(int argc, char* argv[])    //exe  filename
{
    int fd_socket[2];
    int fd_file;
    if(socketpair(AF_LOCAL, SOCK_STREAM, 0, fd_socket) == -1)
    {
        perror("socketpair");
        exit(-1);
    }
    if(fork()>0)    //parent fd[0]
    {
        close(fd_socket[1]);
        signal(SIGCHLD, my_handler);
        fd_file = open(argv[1], O_RDONLY);
        if(fd_file == -1)
        {
            perror("open");
            close(fd_socket[0]);
            close(fd_socket[1]);
            exit(-1);
        }
        send_n(fd_socket[0], fd_file);
        printf("parent fd_file:%d
", fd_file);
        close(fd_file);
        close(fd_socket[0]);
        return;
    }
    else    //child fd[1]
    {
        int fd_to_recv;
        char buf[1024];
        close(fd_socket[0]);
        recv_n(fd_socket[1], &fd_to_recv);
        printf("child recv fd:%d
", fd_to_recv);
        FILE* fp = fdopen(fd_to_recv, "r");
        while(bzero(buf, 1024), fgets(buf, 1024, fp) != NULL)
        {
            printf("%s", buf);
        }
        fclose(fp);
        close(fd_to_recv);
        close(fd_socket[1]);
    }
    return 0;
}
void send_n(int fd_socket, int fd_to_send)
{
    struct msghdr send_msg;
    struct iovec  bufs[1];
    struct cmsghdr *pcmsg;
    char buffer[]="hello world";
    int cmsglen = CMSG_LEN(sizeof(int));
    send_msg.msg_name = NULL;
    send_msg.msg_namelen = 0;
    send_msg.msg_flags = 0;
    bufs[0].iov_base = buffer;
    bufs[0].iov_len = strlen(buffer);
    send_msg.msg_iov = bufs;
    send_msg.msg_iovlen = 1;
    pcmsg = (struct cmsghdr*)calloc(1, cmsglen);
    pcmsg->cmsg_len = cmsglen;
    pcmsg->cmsg_level = SOL_SOCKET;
    pcmsg->cmsg_type = SCM_RIGHTS;
    *(int*)CMSG_DATA(pcmsg) = fd_to_send;
    send_msg.msg_control = pcmsg;
    send_msg.msg_controllen = cmsglen;
    sendmsg(fd_socket, &send_msg, 0);
}

void recv_n(int fd_socket, int* fd_to_recv)
{
    struct msghdr recv_msg;
    struct iovec  bufs[1];
    struct cmsghdr*  pcmsg;
    char buffer[1024]="";
    int cmsglen = CMSG_LEN(sizeof(int));
    pcmsg = (struct cmsghdr*)calloc(1,cmsglen );
    bufs[0].iov_base = buffer;
    bufs[0].iov_len = 1024;
    recv_msg.msg_iov = bufs;
    recv_msg.msg_iovlen = 1;
    recv_msg.msg_control = pcmsg;
    recv_msg.msg_controllen = cmsglen;
    recvmsg(fd_socket, &recv_msg, 0);
    printf("buf:%s
", buffer);
    *fd_to_recv = *(int*)CMSG_DATA(pcmsg);
}