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    管道(pipe)：管道可用于具有亲缘关系的进程间的通信，是一种半双工的方式，数据只能单向流动，允许一个进程和另一个与它有共同祖先的进程之间进行通信。

PIPE模块程序一

下面模块代码是在主函数中创将一个进程，在子进程中往管道中写数据，在父进程中读取数据，也就是一对一的读写操作。

/*============================================================================= #     FileName: pipe1.c#         Desc: an example of pipe communication application#       Author: Licaibiao #      Version:  #   LastChange: 2017-01-09  #      History:  =============================================================================*/#include 
   
    #include 
    
     #include 
     
      #include 
      
       #include 
       
        #include 
        
         int main(int argc, char *argv[]){ pid_t pid; int fd[2]; int read_count = 0; int i; char read_buffer[10] = {0}; char write_buffer[10] = {0}; /*create pipe*/ if (pipe(fd) < 0) { printf("Create pipe failed\n"); return -1; } /*create process*/ if ((pid = fork()) < 0) { printf("Fork failed\n"); return -1; } /* child */ if (pid == 0) { printf("[child]Close read endpoint...\n"); /* close read */ close(fd[0]); for(i=0;i<10;i++) { write_buffer[i]=i; } write(fd[1],write_buffer,i); } /*father*/ else { printf("[parent]Close write endpoint...\n"); /* close write */ close(fd[1]); read_count = read(fd[0], read_buffer, 10); printf("father process read data\n"); for(i=0; i
        
       
      
     
    
   

root@ubuntu:/home/share/pipe# gcc pipe1.c -o testroot@ubuntu:/home/share/pipe# ./test [parent]Close write endpoint...[child]Close read endpoint...father process read dataread_buffer[0] = 0read_buffer[1] = 1read_buffer[2] = 2read_buffer[3] = 3read_buffer[4] = 4read_buffer[5] = 5read_buffer[6] = 6read_buffer[7] = 7read_buffer[8] = 8read_buffer[9] = 9

    下面的程序是在主进程中创建了三个子进程，在子进程中写入数据，在父进程中读出数据，这里使用的是多进程写入，因此需要对文件进程加锁，这里使用的了lockf函数。

/*============================================================================= #     FileName: pipe2.c#         Desc: three process write piep and father process read data#       Author: Licaibiao #      Version:  #   LastChange: 2017-01-09  #      History:  =============================================================================*/#include 
   
    #include 
    
     #include 
     
      #include 
      
       #include 
       
        #include 
        
         #include 
         
          #include 
          
           #include 
           
            int main(void){ int fd[2]; int i; int pid[3]={1,1,1}; char outpipe[100],inpipe[100]; pipe(fd); /* create three process */ for(i=0;i<3;i++) { pid[i]=fork( ); if(pid[i]==0) break; } if(pid[0]==0) { lockf(fd[1],F_LOCK,0); sprintf(outpipe,"child 1 process is sending message!"); write(fd[1],outpipe,50); sleep(5); lockf(fd[1],F_ULOCK,0); exit(0); } if(pid[1]==0) { lockf(fd[1],F_LOCK,0); sprintf(outpipe,"child 2 process is sending message!"); write(fd[1],outpipe,50); sleep(5); lockf(fd[1],F_ULOCK,0); exit(0); } if(pid[2]==0) { lockf(fd[1],F_LOCK,0); sprintf(outpipe,"child 3 process is sending message!"); write(fd[1],outpipe,50); sleep(5); lockf(fd[1],F_ULOCK,0); exit(0); } wait(0); read(fd[0],inpipe,50); printf("%s\n",inpipe); read(fd[0],inpipe,50); printf("%s\n",inpipe); read(fd[0],inpipe,50); printf("%s\n",inpipe); return 0;}
           
          
         
        
       
      
     
    
   

root@ubuntu:/home/share/pipe# gcc pipe2.c -o testroot@ubuntu:/home/share/pipe# ./test child 3 process is sending message!child 2 process is sending message!child 1 process is sending message!root@ubuntu:/home/share/pipe# ./test child 3 process is sending message!child 2 process is sending message!child 1 process is sending message!root@ubuntu:/home/share/pipe# ./test child 3 process is sending message!child 2 process is sending message!child 1 process is sending message!root@ubuntu:/home/share/pipe# ./test child 2 process is sending message!child 3 process is sending message!child 1 process is sending message!root@ubuntu:/home/share/pipe# ./test child 3 process is sending message!child 2 process is sending message!child 1 process is sending message!root@ubuntu:/home/share/pipe# ./test child 3 process is sending message!child 2 process is sending message!child 1 process is sending message!root@ubuntu:/home/share/pipe# ./test child 3 process is sending message!child 2 process is sending message!child 1 process is sending message!root@ubuntu:/home/share/pipe# ./test child 3 process is sending message!child 2 process is sending message!child 1 process is sending message!root@ubuntu:/home/share/pipe# ./test child 1 process is sending message!child 3 process is sending message!child 2 process is sending message!root@ubuntu:/home/share/pipe#

PIPE模块程序三

下面的程序是两个进程写入，两个进程读取，在pipe中写入的数据，其他的进程再读取的时候，将读取不到数据。程序代码如下：

/*============================================================================= #     FileName: pipe3.c#         Desc: two process write into pipe and two process read from pipe#       Author: Licaibiao #      Version:  #   LastChange: 2017-01-09  #      History: =============================================================================*/#include 
   
    #include 
    
     #include 
     
      #include 
      
       #include 
       
        #include 
        
         #include 
         
          #include 
          
           #include 
           
            int main(void){ int fd[2], i; int pid[3] = {1,1,1}; char outpipe[100],inpipe[100]; pipe(fd); for(i=0;i<3;i++){ pid[i]=fork( ); if(pid[i]==0) break; } if(pid[0]==0) { lockf(fd[1],F_LOCK,0); sprintf(outpipe,"child 1 process is sending message!"); write(fd[1],outpipe,50); sleep(5); lockf(fd[1],F_ULOCK,0); exit(0); } if(pid[1]==0) { lockf(fd[1],F_LOCK,0); sprintf(outpipe,"child 2 process is sending message!"); write(fd[1],outpipe,50); sleep(5); lockf(fd[1],F_ULOCK,0); exit(0); } if(pid[2]==0) { lockf(fd[0],F_LOCK,0); read(fd[0],inpipe,50); printf("Child 3 read:\n%s\n",inpipe); lockf(fd[0],F_ULOCK,0); exit(0); } wait(0); read(fd[0],inpipe,50); printf("Parent read:\n%s\n",inpipe); exit(0);}
           
          
         
        
       
      
     
    
   

root@ubuntu:/home/share/pipe# vim pipe3.c root@ubuntu:/home/share/pipe# gcc pipe3.c -o test root@ubuntu:/home/share/pipe# ./test Child 3 read:child 2 process is sending message!Parent read:child 1 process is sending message!root@ubuntu:/home/share/pipe# ./test Child 3 read:child 2 process is sending message!Parent read:child 1 process is sending message!root@ubuntu:/home/share/pipe# ./test Child 3 read:child 2 process is sending message!Parent read:child 1 process is sending message!root@ubuntu:/home/share/pipe# ./test Child 3 read:child 2 process is sending message!Parent read:child 1 process is sending message!

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