#include <unistd.h>#include <sys/types.h>#include <errno.h>int main(){	int pipe_fd[2];	pid_t pid;	char r_buf[4];	char* w_buf;		int writenum;	int cmd;		memset(r_buf,0,sizeof(r_buf));	if(pipe(pipe_fd)<0)	{		printf("pipe create error\n");		return -1;	}	if((pid=fork())==0)	{		printf("In child process\n");		close(pipe_fd[0]);		close(pipe_fd[1]);		sleep(10);		exit(0);			}	else if(pid>0)	{		sleep(1);		printf("In parent process\n");		//close(pipe_fd[0]);		w_buf="111";		if((writenum=write(pipe_fd[1],w_buf,4))==-1)		{			printf("write to pipe error\n");		}		else		{			printf("the bytes write to pipe is %d \n",writenum);		}		close(pipe_fd[1]);	}		return 0;}