Linux C 怎么检测网络状态

#include <stdio.h>
#include<unistd.h>
#include<string.h> 

ping_check (char *gateway_str)
{
   printf("ping_check ::gateway_str -- %s\n",gateway_str);
    FILE *fp;
    size_t len = 0;
    char *pos;
    int ret,percent = 100;
    char* line = NULL;  char cmd[80]={0};
 sprintf(cmd, "ping -c 1 -q -n %s >ping_gatway.txt",gateway_str);
    system(cmd);
    fp = fopen("ping_gatway.txt", "r");
    if (!fp){
        goto error1;
    }
    while (getline (&line, &len, fp) != -1)   {
   if (strncmp ("packets transmitted", line + 2, 19) != 0)
       {
            continue;
       }
        pos = strchr (line, '%');
        if (pos == 0) {
            goto error1;
        }
        while (*pos != ' ')
            {   
              pos--;
            }
        sscanf (pos, " %d%% loss", &percent);
        printf("ping_check->pos -- %s\n", pos, );
        printf("ping_check->percent -- %d \n", percent);
        if (percent == 0)   {
            printf("ping_check:OK\n");
            ret = PING_TEST_IPV6_OK;
        }else {
            printf("ping_check: NGNG \n");
            }
       }

    error1:
     free(line);
     ping_err_ipv6 = ret;
     printf ("ping_check:ret =%d\n",ret);
     return ret;
}