有名管道_3

编程实现3人间相互通信

思路：需要防止打开管道时，陷入死锁。

总共需要建立3对管道，6个管道。每两个用户之间都有一对管道。一个用户有2个读端和2个写端。

:1             :2               :3

1-2  w       1-2  r          1-3 r

1-3  w       2-1 w          3-1 w

2-1  r        2-3 w          2-3 r

3-1  r        3-2 r           3-2 w

注意

此处每个用户，都是fork出2个子进程，总共3个进程。其中2个进程用于分别接收另外两个用户的消息，1个进程负责向其余两个用户发送消息。

不管fork出多少个进程，每个进程都要专注做自己的事情。此处每次fork出一个新进程，该进程都会拥有与父进程相同的4个文件描述符。我们只使用我们需要的那个，关闭其余3个不需要的。

再次强调，每个进程都要专注做自己的事情。

1.c

/*************************************************************************
    > File Name: 1.c
    > Author: KrisChou
    > Mail:zhoujx0219@163.com 
    > Created Time: Fri 22 Aug 2014 08:29:12 PM CST
 ************************************************************************/


#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdlib.h>
#include <string.h>
int main(int argc, char* argv[])//EXE 12 13 21 31
{
    if(mkfifo(argv[1],0666) == -1 || mkfifo(argv[2], 0666) == -1)
    {
        perror("mkfifo");
        exit(1);
    }
    int fd_12, fd_13, fd_21, fd_31 ;
    char buf_123[1024],buf_21[1024],buf_31[1024];
    fd_12 = open(argv[1], O_WRONLY);
    fd_13 = open(argv[2], O_WRONLY);
    fd_21 = open(argv[3], O_RDONLY);
    fd_31 = open(argv[4], O_RDONLY);
    printf("open sucess ! \n");
    if(fork() == 0) //child1  recv from 2
    {
        close(fd_12);
        close(fd_13);
        close(fd_31);
        while(memset(buf_21, 0, 1024), read(fd_21, buf_21, 1024) > 0)
        {
            printf("from 2: ");
            write(1, buf_21, strlen(buf_21));
        }
        close(fd_21);
        exit(1);
    }
    if(fork() == 0)// child2  recv from 3
    {
        close(fd_12);
        close(fd_13);
        close(fd_21);
        while(memset(buf_31, 0, 1024), read(fd_31, buf_31, 1024) > 0)
        {
            printf("from 3: ");
            write(1, buf_31, strlen(buf_31));
        }
        close(fd_31);
        exit(1);
    }
    close(fd_21);
    close(fd_31);
    while(memset(buf_123, 0, 1024), fgets(buf_123, 1024, stdin) != NULL)
    {
        write(fd_12, buf_123, strlen(buf_123));
        write(fd_13, buf_123, strlen(buf_123));
    }
    close(fd_12);
    close(fd_13);
    wait(NULL);
    wait(NULL);
    unlink(argv[1]);
    unlink(argv[2]);
    return 0 ;
}

2.c

/*************************************************************************
    > File Name: 1.c
    > Author: KrisChou
    > Mail:zhoujx0219@163.com 
    > Created Time: Fri 22 Aug 2014 08:29:12 PM CST
 ************************************************************************/


#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdlib.h>
#include <string.h>
int main(int argc, char* argv[])//EXE 12 21 23 32
{
    if(mkfifo(argv[2],0666) == -1 || mkfifo(argv[3], 0666) == -1)
    {
        perror("mkfifo");
        exit(1);
    }
    int fd_12, fd_21, fd_23, fd_32 ;
    char buf_213[1024],buf_32[1024],buf_12[1024];
    fd_12 = open(argv[1], O_RDONLY);
    fd_21 = open(argv[2], O_WRONLY);
    fd_23 = open(argv[3], O_WRONLY);
    fd_32 = open(argv[4], O_RDONLY);
    printf("open sucess ! \n");
    if(fork() == 0) //child2  recv from 1
    {
        close(fd_21);
        close(fd_23);
        close(fd_32);
        while(memset(buf_12, 0, 1024), read(fd_12, buf_12, 1024) > 0)
        {
            printf("from 1: ");
            write(1, buf_12, strlen(buf_12));
        }
        close(fd_12);
        exit(1);
    }
    if(fork() == 0)// child2  recv from 3
    {
        close(fd_12);
        close(fd_21);
        close(fd_23);
        while(memset(buf_32, 0, 1024), read(fd_32, buf_32, 1024) > 0)
        {
            printf("from 3: ");
            write(1, buf_32, strlen(buf_32));
        }
        close(fd_32);
        exit(1);
    }
    close(fd_12);
    close(fd_32);
    while(memset(buf_213, 0, 1024), fgets(buf_213, 1024, stdin) != NULL)
    {
        write(fd_21, buf_213, strlen(buf_213));
        write(fd_23, buf_213, strlen(buf_213));
    }
    close(fd_21);
    close(fd_23);
    wait(NULL);
    wait(NULL);
    unlink(argv[2]);
    unlink(argv[3]);
    return 0 ;
}

3.c

/*************************************************************************
    > File Name: 1.c
    > Author: KrisChou
    > Mail:zhoujx0219@163.com 
    > Created Time: Fri 22 Aug 2014 08:29:12 PM CST
 ************************************************************************/


#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdlib.h>
#include <string.h>
int main(int argc, char* argv[])//EXE 13 31 23 32
{
    if(mkfifo(argv[2],0666) == -1 || mkfifo(argv[4], 0666) == -1)
    {
        perror("mkfifo");
        exit(1);
    }
    int fd_13, fd_31, fd_23, fd_32 ;
    char buf_312[1024],buf_13[1024],buf_23[1024];
    fd_13 = open(argv[1], O_RDONLY);
    fd_31 = open(argv[2], O_WRONLY);
    fd_23 = open(argv[3], O_RDONLY);
    fd_32 = open(argv[4], O_WRONLY);
    printf("open sucess ! \n");
    if(fork() == 0) //child1  recv from 1
    {
        close(fd_31);
        close(fd_23);
        close(fd_32);
        while(memset(buf_13, 0, 1024), read(fd_13, buf_13, 1024) > 0)
        {
            printf("from 1: ");
            write(1, buf_13, strlen(buf_13));
        }
        close(fd_13);
        exit(1);
    }
    if(fork() == 0)// child2  recv from 2
    {
        close(fd_13);
        close(fd_31);
        close(fd_32);
        while(memset(buf_23, 0, 1024), read(fd_23, buf_23, 1024) > 0)
        {
            printf("from 2: ");
            write(1, buf_23, strlen(buf_23));
        }
        close(fd_23);
        exit(1);
    }
    close(fd_13);
    close(fd_23);
    while(memset(buf_312, 0, 1024), fgets(buf_312, 1024, stdin) != NULL)
    {
        write(fd_31, buf_312, strlen(buf_312));
        write(fd_32, buf_312, strlen(buf_312));
    }
    close(fd_31);
    close(fd_32);
    wait(NULL);
    wait(NULL);
    unlink(argv[2]);
    unlink(argv[4]);
    return 0 ;
}

运行，分别打开3个终端，分别输入：

./1.exe 12.fifo 13.fifo 21.fifo 31.fifo
./2.exe 12.fifo 21.fifo 23.fifo 32.fifo
./3.exe 13.fifo 31.fifo 23.fifo 32.fifo