linux下读取管道 总是返回1

C/C++ code:

#include <unistd.h>
#include <sys/types.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>

int main()
{
int pipe_fd[2];
pid_t pid;
char buf_r[100];
char* p_wbuf;
ssize_t r_num;
memset(buf_r,0,sizeof(buf_r));
if ( pipe(pipe_fd)< 0 )
{
printf("pipe create error\n");
return -1;
}
if ( (pid = fork())==0 )
{
printf(" i'm in child process\n");
close(pipe_fd[1]);
sleep (2);
if( (r_num = read(pipe_fd[0],buf_r,100)>0) ){
printf("%u numbers read from the pipe is %s\n",r_num,buf_r);
}
close(pipe_fd[0]);
exit(0);
}
else if(pid > 0){
printf("i'm in parent process\n");
close(pipe_fd[0]);
if( (write(pipe_fd[1],"hello",5)!=-1) ){
printf("parent write1 success\n");
}
if( (write(pipe_fd[1]," pipe",5)!=-1) ){
printf("parent write2 success\n");
}
close(pipe_fd[1]);
//sleep(3);
waitpid(pid,NULL,0); /*wait for pid process done*/
exit(0);
}
return 0;
}



为什么总是返回1？谢谢啦

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