select.c

来自「《嵌入式Linux应用程序开发详解》一书的源代码之第六章」· C语言 代码 · 共 55 行

/*select.c*/
#include <fcntl.h>
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <time.h>

int main(void)
{
	int fds[2];
	char buf[7];
	int i,rc,maxfd;
	fd_set inset1,inset2;
	struct timeval tv;
	if((fds[0] = open ("hello1", O_RDWR|O_CREAT,0666))<0)
		perror("open hello1");
	if((fds[1] = open ("hello2", O_RDWR|O_CREAT,0666))<0)
		perror("open hello2");
	if((rc = write(fds[0],"Hello!\n",7)))
		printf("rc=%d\n",rc);
	lseek(fds[0],0,SEEK_SET);
	maxfd = fds[0]>fds[1] ? fds[0] : fds[1];
	FD_ZERO(&inset1); 
	FD_SET(fds[0],&inset1);
	FD_ZERO(&inset2);
	FD_SET(fds[1],&inset2);
	tv.tv_sec=2;
	tv.tv_usec=0;
	while(FD_ISSET(fds[0],&inset1)||FD_ISSET(fds[1],&inset2)){ 
		if(select(maxfd+1,&inset1,&inset2,NULL,&tv)<0) 
			perror("select");
		else{
			if(FD_ISSET(fds[0],&inset1)){
				rc = read(fds[0],buf,7);
				if(rc>0){
					buf[rc]='\0';
					printf("read: %s\n",buf);
				}else
					perror("read");
			}
			if(FD_ISSET(fds[1],&inset2)){
				rc = write(fds[1],buf,7);
				if(rc>0){
					buf[rc]='\0';
					printf("rc=%d,write: %s\n",rc,buf);
				}else
					perror("write");
			sleep(10);
			}
		}
	}
	exit(0);
}