一、用select监听多个文件描述符
题目表述：监听鼠标和键盘的变化
标准模板
#include <stdio.h>
#include <stdlib.h>
#include <sys/time.h>
#include <unistd.h>
#include <sys/types.h>
#include <fcntl.h>
#include <sys/stat.h>
int main(int argc, char const *argv[])
{
struct timeval time;
fd_set r_set;
fd_set all_set;
time.tv_sec = 3;
time.tv_usec = 0;
int fd;
int fds[1024];
for (size_t i = 0; i < 1024; i++)
{
fds[i] = -1;
}
if((fd = open("/dev/input/mouse0", O_RDWR | O_CREAT, 0655)) < 0)
{
perror("open file error!");
exit(1);
}
FD_SET(fd, &r_set);
for (size_t i = 0; i < 1024; i++)
{
if (fds[i] == -1)
{
fds[i] = fd;
break;
}
}
FD_SET(0, &r_set);
for (size_t i = 0; i < 1024; i++)
{
if (fds[i] == -1)
{
fds[i] = 0;
break;
}
}
all_set = r_set;
while (1)
{
r_set = all_set;
int ret = select(fd + 1, &r_set, NULL, NULL, NULL);
if (ret == -1)
{
perror("select error");
exit(1);
}
for (size_t i = 0; i < 1024; i++)
{
if (fds[i] != 1)
{
if (FD_ISSET(fds[i], &r_set) > 0)
{
if (fds[i] == fd)
{
int cor;
read(fd, &cor, sizeof(cor));
printf("cor = %d\n", cor);
}
else if(fds[i] == 0)
{
char buffer[1024];
read(0, buffer, sizeof(buffer));
printf("buffer = %s\n", buffer);
}
if (--ret == 0)
{
break;
}
}
}
}
}
return 0;
}
二、select的优缺点
- 缺点1
FD_SET最大1024，如FD_SETSIZE
最多监听1024，监听范围受限 - 缺点2
轮询：全盘轮询；效率最低
优点：可以跨平台（Windows和Linux都可以）