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poll.md

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Poll Back

  • poll()与select()實現的功能相似, 能監聽多個文件描述符. poll()能監聽特定的某個文件描述符其返回事件
  • poll()比select()更具有細緻的分類
  • poll()效率要比select()高
method
/* select */
unsigned int poll(struct pollfd* __fds, nfds_t __nfds, int __timeout)

/* pollfd */
struct pollfd
{
	int fd;
	short int events;	//expected events 	
	short int revents;	//return events
}
parameters
  • pollfd: 設置監聽的文件描述符和期待的事件
  • nfds: 文件描述符的個數
  • timeout: 指定測試時間閾值上界
    • NULL: forever
    • >0: time
    • 0: return immediately after check, without waiting
return value
  • num: the number of ready descriptors
  • 0: timeout but none is ready
  • -1: failure
  • errno: wrong code