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：

网卡是否存在；
网卡是否down；
网卡UP，插了网线(RUNNING)；
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