本来想验证一下管道的写端对读端有倚赖.但是写出来的代码却不是想要的效果.
不知道是程序写的有毛病还是本人对管道理解的有偏颇,还请高手指点. 

代码如下:     

      1 #include 
      2 #include 
      3
      4 #define BUFFSIZE        2*1024
      5 int main(void)
      6 {
      7         int pipe_fd[2];
      8         int ret;
      9         char buf[BUFFSIZE];
     10         int pid;
     11
     12         if ((ret = pipe(pipe_fd)) == -1)
     13         {
     14                 fprintf(stderr,"pipe creat error!n");
     15                 exit(0);
     16         }
     17
     18         if ((pid = fork())  0)
     31         {
     32                 close(pipe_fd[0]);//close read fd
     33
     34                 if ((ret = write(pipe_fd[1],"This is a test!n",30)) == -1)
     35                 {
     36                         fprintf(stderr,"write error!n");
     37                         exit(0);
     38                 }
     39                 else
     40                         printf("write %d byte to pipen",ret);
     41                 close(pipe_fd[1]);
     42                 return 0;
     43         }
                                                                                                                                 44}
环境: REDHAT AS4(kernel 2.6.18) + gcc 3.4.3
结果如下(运行了20次):

-bash-3.00# ls
pipe_write_only  pipe_write_only.c  source
-bash-3.00# ./pipe_write_only
-bash-3.00# ./pipe_write_only
write 30 byte to pipe
-bash-3.00# ./pipe_write_only
-bash-3.00# ./pipe_write_only
-bash-3.00# ./pipe_write_only
-bash-3.00# ./pipe_write_only
write 30 byte to pipe
-bash-3.00# ./pipe_write_only
-bash-3.00# ./pipe_write_only
write 30 byte to pipe
-bash-3.00# ./pipe_write_only
-bash-3.00# ./pipe_write_only
-bash-3.00# ./pipe_write_only
-bash-3.00# ./pipe_write_only
-bash-3.00# ./pipe_write_only
-bash-3.00# ./pipe_write_only
-bash-3.00# ./pipe_write_only
-bash-3.00# ./pipe_write_only
-bash-3.00# ./pipe_write_only
-bash-3.00# ./pipe_write_only
-bash-3.00# ./pipe_write_only
write 30 byte to pipe
-bash-3.00# ./pipe_write_only
-bash-3.00#

L25,L26和L32,L34抢时间的问题吧。
要验证就要在L32前先sleep(1)，
你再试试看。
现有的代码不能保证L32,L34在L25,L26之后执行。

供参考。
请多注意多进程多线程的同步问题。