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初学linux,有个问题想请教
这是一个关于管道的c程序:
#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;
int 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("pid0=%d\n",pid);
printf("\n");
close(pipe_fd[1]);
sleep(2);
if((r_num=read(pipe_fd[0],buf_r,100))>0)
{
printf("%dnumbers read from the pipe is %s\n",r_num,buf_r);
}
close(pipe_fd[0]);
exit(0);
}
else if(pid>0)
{
printf("pid=%d\n",pid);
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]);
printf("pid=%d\n",pid);
sleep(3);
waitpid(pid,NULL,0);
exit(0);
}
}
这是它的一次运行结果:
我对它的运行顺序搞不懂,这个运行结果不是按程序顺序执行的,为什么?
望高手给于解答,谢谢 |
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