首页 > 代码库 > linux poll
linux poll
man poll:
NAME
poll, ppoll - wait for some event on a file descriptor
SYNOPSIS
#include <poll.h>
int poll(struct pollfd *fds, nfds_t nfds, int timeout);
#define _GNU_SOURCE /* See feature_test_macros(7) */
#include <poll.h>
int ppoll(struct pollfd *fds, nfds_t nfds,
const struct timespec *timeout_ts, 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 per‐
form 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 */
};
要测试的条件由events指定，函数在相应的revents成员中返回该描述字的状态。（每个描述字都有两个变量，一个为调用值，另一个为返回结果，从而避免使用值结果参数。）
结果数组中元素的个数由nfds参数指定。
返回值：当发生错误时，poll函数的返回值为-1，若定时器时间到之前没有任何描述字就绪，则返回0.否则返回就绪描述字的个数，即其revents成员值非0的描述字个数。
如果我们不再关心某个特定描述字，那么可以把与它对应的pollfd结构的fd成员设置为一个负值。poll函数将忽略这样的pollfd结构的events成员，返回时将它的revents成员的值置为0.
020.#ifndef INFTIM /*按照书上解释：POSIX规范要求INFTIM在头文件<poll.h>中定义，不过*/
021.#define INFTIM -1 /*许多系统仍然把它定义在头文件<sys/stropts.h>中，但是经过我的测试*/
022.#endif /*即使都包含这两个文件，编译器也找不到，不知何解。索性自己定义了。*/
#include"unp.h"#include<limits.h>//for open_MAX,ubuntu?бû?#define OPEN_MAX 1024#define INFTIM -1int main(int argc,char **argv){ int i ,maxi,listenfd,connfd,sockfd; int nready; ssize_t n; socklen_t clilen; char buf[MAXLINE]; struct pollfd client[OPEN_MAX]; struct sockaddr_in cliaddr,servaddr; listenfd=Socket(AF_INET,SOCK_STREAM,0); bzero(&servaddr,sizeof(servaddr)); servaddr.sin_family=AF_INET; servaddr.sin_port=htons(8001); servaddr.sin_addr.s_addr=htonl(INADDR_ANY); Bind(listenfd,(SA*)&servaddr,sizeof(servaddr)); Listen(listenfd,LISTENQ); client[0].fd=listenfd; client[0].events=POLLRDNORM; for(i=1;i<OPEN_MAX;i++) client[i].fd=-1;// maxi=0; for(;;) { nready=poll(client,maxi+1,INFTIM); if(client[0].revents & POLLRDNORM ) { //new client connction clilen=sizeof(cliaddr); connfd=Accept(listenfd,(SA*)&cliaddr,&clilen); for(i=1;i<OPEN_MAX;i++) { if(client[i].fd<0) { client[i].fd=connfd;//save desc break; } } if(i==OPEN_MAX) err_quit("too many client"); client[i].events=POLLRDNORM; if(i>maxi) maxi=i; if(--nready<=0) continue; } for(i=1;i<=maxi;i++) { //check all clients for data if( (sockfd=client[i].fd)<0) continue; if(client[i].revents & ( POLLRDNORM | POLLERR)) { if((n=read(sockfd,buf,MAXLINE))<0) { if(errno==ECONNRESET) { //conncetion reset by client Close(sockfd); client[i].fd=-1; } else err_sys("read error"); } else if(n==0) { //connection close by client Close(sockfd); client[i].fd=-1; } else Writen(sockfd,buf,n); if(--nready<=0) break; } } }}
http://itlab.idcquan.com/linux/c/816050.html
linux poll