poll 结构体相关定义

/* sys/poll.h */
/* 文件描述符数量 */
typedef unsigned long int nfds_t;/* 
* 轮训请求的数据结构体定义 
* fd : 待轮训的描述符
* events : poll 轮询关心的事件类型
* revents : 实际发生的事件类型
*/
struct pollfd
{int fd;short int events;short int revents;
}；/*
* 函数定义
* *fds : struct pollfd 结构体
* nfds : 轮询描述符的数量
* timeout : 轮询的时间
*/
int poll(struct pollfd *fds, nfds_t nfds, int timeout)/*
* bits/poll.h
* 事件类型,这些bits用于设置events来指定感兴趣的事件类型，在revents中指示文件描述符状态。
*/
#define POLLIN     0X001        /* 有数据待读 there is data to read. */
#define POLLPRI    0X002        /* 有紧急的数据待读 there is urgent data to read. */
#define POLLOUT    0X004        /* 现在写将不会被阻塞 writing now will not block. *//* these value are defined in XPG4.2 */
#define POLLRDNORM    0x040    /* normal data may be read. */
#define POLLRDBAND    0X080    /* priority data may be read. */
#define POLLWRNORM    0X100    /* writing now will be block. */
#define POLLWEBAND    0X200    /* priority data may be written. *//* these are extensions for Linux */
#define POLLMSG       0X400
#define POLLREMOVE    0X1000
#define POLLRDHUP     0X2000/* 事件类型将被隐式轮询，不需要设置events， 但是会在revents中指定描述符状态 */
#define POLLERR        0x008    /* error condition. */
#define POLLHUP        0X010    /* HUNG UP */
#define POLLNVAL       0X020    /* invalid polling request. */    

poll 函数使用

int fd;
int ret;
struct pollfd  fdset[1];
nfds_t nfds;fd = open(device,type);while(1){memset((void *)fdset,0x0,sizeof(fdset));fdset.fd = fd;fdset.events = POLLPRI;ret = poll(fdset,nfds, 2000)if(ret < 0){printf("poll err!");}else if(ret == 0){printf("polling...");}else{//相关操作}
}