阻塞型看:阻塞IO读数据
使用set_fl(STDIN_FILENO, O_NONBLOCK);
将输入输出设置为非阻塞时,read()函数等不到数据输入的时候就会直接返回出错信息,而不是继续等到用户输入。
#include <unistd.h>
#include <fcntl.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
int main(void)
{
char buffer[4096] = {'\0'}; //因为使用电脑的缓存区大小是4096
ssize_t size = 0;
//设置非阻塞形式IO
set_fl(STDIN_FILENO, O_NONBLOCK);
sleep(5);
size = read(STDIN_FILENO, buffer, sizeof(buffer));
if(size < 0)
{
perror("read error!");
exit(1);
}
else if(size == 0)
{
printf("read finished!\n");
}
else
{
if(write(STDOUT_FILENO, buffer, size) != size)
{
perror("write error!");
exit(1);
}
}
return 0;
}
void set_fl(int fd, int flags) /* flags are file status flags to turn on */
{
int val;
if ( (val = fcntl(fd, F_GETFL, 0)) < 0)
{
printf("fcntl F_GETFL error");
exit(1);
}
val |= flags; /* turn on flags */
//重新设置文件状态标志(val为新文件的文件状态标志)
if (fcntl(fd, F_SETFL, val) < 0)
{
printf("fcntl F_SETFL error");
exit(1);
}
}
void clr_fl(int fd, int flags)
{
int val;
if ((val = fcntl(fd, F_GETFL, 0)) == -1)
{
perror("fcntl error!");
exit(1);
}
val &= ~flags; /* turn flags off */
if (fcntl(fd, F_SETFL, val) == -1)
{
perror("fcntl error!");
exit(1);
}
return;
}
测试;
andrew@andrew-Thurley:~/work/iotec$ bin/noblock
read error!: Resource temporarily unavailable
andrew@andrew-Thurley:~/work/iotec$