目录

1.说明

2.解析命令法：

2.1.CODE

2.2.TEST

3.SOCKET法

1.说明

        此代码主要对Linux下网卡4种状态进行检测，可以检查：

1. 网卡是否存在；
2. 网卡是否down；
3. 网卡UP，插了网线(RUNNING)；
4. 网卡UP，没有插网线 

2.解析命令法：

2.1.CODE

#define BUFSIZ 256
/*check if_name status
 *if not exist,return 0
 *if exist and down,return 1
 *if up and notlink,return 2
 *if up and link,	return 3
 */
int get_if_status(char *if_name)
{
	char buffer[BUFSIZ];
	char cmd[100];
	FILE *read_fp;
	int chars_read;	
	int ret =0;
	memset( buffer, 0, BUFSIZ );
	memset( cmd, 0, 100 );
	sprintf(cmd, "ifconfig -a | grep %s",if_name);
	read_fp = popen(cmd, "r");
	
	if ( read_fp != NULL )
	{
		chars_read = fread(buffer, sizeof(char), BUFSIZ-1, read_fp);
		pclose(read_fp);
		if (chars_read > 0)
		{
			ret = 1;	/*if_name exist*/
		}
		else
		{
			fprintf(stderr, "%s: NO FOUND\r\n",if_name);
			return 0;	/*if_name not exist*/
		}
	}
	if(ret == 1)
	{
		memset( buffer, 0, BUFSIZ );
		memset( cmd, 0, 100 );
		sprintf(cmd, "ifconfig | grep %s",if_name);
		read_fp = popen(cmd, "r");
		if ( read_fp != NULL )
		{
			chars_read = fread(buffer, sizeof(char), BUFSIZ-1, read_fp);
			pclose(read_fp);
			if (chars_read > 0)
			{
				ret = 2;	/*if_name exist and up*/
			}
			else
			{
				fprintf(stderr, "%s: DOWN\r\n",if_name);
				return 1;	/*if_name exist but down*/
			}
		}
	}
	if(ret == 2)
	{
		memset( buffer, 0, BUFSIZ );
		memset( cmd, 0, 100 );
		sprintf(cmd, "ifconfig %s | grep RUNNING | awk '{print $3}'",if_name);
		read_fp = popen(cmd, "r");
		if ( read_fp != NULL )
		{
			chars_read = fread(buffer, sizeof(char), BUFSIZ-1, read_fp);
			pclose(read_fp);
			if (chars_read > 0)
			{
				fprintf(stderr, "%s: LINKED\r\n",if_name);	
				return 3;	/*if_name up and link*/
			}
			else
			{
				fprintf(stderr, "%s: UNPLUGGED\r\n",if_name);
				return 2;	/*if_name up and notlink*/
			}
		}
	}
	return -1;
}
int main(int argc, char* argv[])
{
	int i=0;
	if(argc != 2)
	{
		fprintf(stderr, "usage: %s ", argv[0]);
		return -1;
	}
	i = get_if_status(argv[1]);
	printf( "if_status = %d\n", i );
	return 0;
}

2.2.TEST

# ./netlink eth100
eth100: NO FOUND
if_status = 0
#

# ifconfig eth0 down
# ./netlink eth0
eth0: DOWN
if_status = 1
#

# ifconfig eth0 up
# ./netlink eth0
eth0: UNPLUGGED
if_status = 2
#

# ./netlink eth0
eth0: LINKED
if_status = 3

3.SOCKET法

        是通过socket解析网卡当前状态，来判断网卡是否存在。

实际实现过程是通过socket获取网卡的SIOCGIFFLAGS属性，判断其IFF_UP属性即可。

 SIOCGIFFLAGS属性：