select函数的使用举例

#include <sys/types.h>
#include <sys/time.h>
#include <stdio.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <unistd.h>

int main()
{
char buffer[128];
int result, nread;
fd_set inputs, testfds;
struct timeval timeout;
FD_ZERO(&inputs);//用select函数之前先把集合清零
FD_SET(0, &inputs);//把要检测的句柄——标准输入（0），加入到集合里。
while(1)
{
testfds = inputs;
timeout.tv_sec = 2;
timeout.tv_usec = 500000;
result = select(FD_SETSIZE, &testfds, (fd_set *)0, (fd_set *)0, &timeout);
switch(result)
{
case 0:
printf("timeout\n");
break;
case -1:
perror("select\n");
return 1;
default:
if(FD_ISSET(0, &testfds))
{
ioctl(0, FIONREAD, &nread);//取得从键盘输入字符的个数，包括回车。
if(nread == 0)
{
printf("keyboard done\n");
return 0;
}
nread = read(0, buffer, nread);
buffer[nread] = 0;
printf("read %d from keyboard: %s", nread, buffer);
}
break;
}
}
return 0;
}