poll函数操作fd,等待读取失败.怎么修改程序?

[learnxml163]

1. 创建两个fifo，用于读入数据.
2. main函数进入poll循环，监视这两个fd
3. 当poll返回>0的时候，读取管道的内容并打印

从命令行,用echo命令向myfifo1/myfifo2发送数据，我期待a.out立刻将数据打印出来。但是a.out阻塞了，什么输出也没有。
我的代码问题在哪里?

#include<sys/stat.h>
#include<sys/types.h>
#include<poll.h>
#include<fcntl.h>
#include<stdio.h>
#include<stdlib.h>
#include<unistd.h>
char buf[20]={0};
int f(const char* fifo){
  unlink(fifo);
  mkfifo(fifo,0666);
  return open(fifo,O_RDONLY);
}
void g(int fd){
  read(fd,buf,sizeof(buf));
  printf("read done:%s\n",buf);
}
int main(void){
  int fd1=f("myfifo1");
  int fd2=f("myfifo2");
  if(!(fd1||fd2))return 1;
  struct pollfd myfifo[2];
  myfifo[0].fd=fd1;
  myfifo[0].events=POLLIN;
  myfifo[1].fd=fd2;
  myfifo[1].events=POLLIN;
  int ret;
  while(ret=poll(myfifo,fd2+1,-1)){
    if(ret<=0){
      perror("poll error\n");
      return 1;
    }else{
      if(     myfifo[0].revents & POLLIN){g(fd1);}
      else if(myfifo[0].revents & POLLIN){g(fd2);}
    }
  }
  close(fd1);
  close(fd2);
  return 0;
}

[justkk]

while(ret=poll(myfifo,fd2+1,-1))
===》
while((ret=poll(myfifo,fd2+1,-1)))

[learnxml163]

[Quote=引用 1 楼 justkk 的回复:]

while(ret=poll(myfifo,fd2+1,-1))
===》
while((ret=poll(myfifo,fd2+1,-1)))
[/Quote]

谢谢，我按照你说的改了。但是问题仍然存在。

[guoxuqu]

while(ret=poll(myfifo,fd2+1,-1))错误应为while(ret=poll(myfifo,2,-1))

[guoxuqu]

#include <poll.h>

int poll(struct pollfd *fds, nfds_t nfds, int timeout);

#define _GNU_SOURCE
#include <poll.h>

int ppoll(struct pollfd *fds, nfds_t nfds,
const struct timespec *timeout, const sigset_t *sigmask);

DESCRIPTION
poll() performs a similar task to select(2): it waits for one of a set
of file descriptors to become ready to perform I/O.

The set of file descriptors to be monitored is specified in the fds
argument, which is an array of structures of the following form:

struct pollfd {
int fd; /* file descriptor */
short events; /* requested events */
short revents; /* returned events */
};

The caller should specify the number of items in the fds array in nfds.
上面是man手册关于poll的说明，最后一句是说poll第二个参赛应该是数组fds的大小

[guoxuqu]

还有一个问题。open(fifo,O_RDONLY);要改为oopen(fifo,O_RDONLY|O_NONBLOCK);
不然会阻塞在这里。