#include <unistd.h>

 #include <stdio.h>

 #include <stdlib.h>

 #include <fcntl.h>

 #include <limits.h>

 #include <sys/types.h>

 #define BUFSZ PIPE_BUF  /*PIPE_BUF管道默认一次性读写的数据长度*/

 int main ( void )

 {

     int fd[];

     char buf[BUFSZ];

     pid_t pid;

     ssize_t len;

     if ( (pipe(fd)) <  ){                        /*创建管道*/

         perror ( "failed to pipe" );

         exit(  );

     }

     if ( (pid = fork()) <  ){                    /* 创建一个子进程 */

         perror ( "failed to fork " );

         exit(  );

     }

     else if ( pid >  ){

         close ( fd[] );                        /*父进程中关闭管道的读出端*/

         write (fd[], "hello tian chaoooo!\n",  );    /*父进程向管道写入数据*/

         exit ();

     }

     else {

         close ( fd[] );                        /*子进程关闭管道的写入端*/

         len = read (fd[], buf, BUFSZ );        /*子进程从管道中读出数据*/

         if ( len <  ){

             perror ( "process failed when read a pipe " );

             exit(  );

         }

         else

             write(STDOUT_FILENO, buf, len);    /*输出到标准输出*/

         exit();

     }

 }