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/*select.c*/
#include <fcntl.h>
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/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=%dn",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]='';
printf("read: %sn",buf);
}else
perror("read");
}
if(FD_ISSET(fds[1],&inset2))
{
rc = write(fds[1],buf,7);
if(rc>0)
{
buf[rc]='';
printf("rc=%d,write: %sn",rc,buf);
}else
perror("write");
sleep(10);
}
}
}
exit(0);
}
视频里历程,为啥视频里编出来是每隔10秒从文件1里读出一行写入文件2.我在Fedora里编完是只读一次然后每隔10s一直写入文件2同一个字符串。难道read函数是阻塞型的?读完一次就一直阻塞? |
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