判断接口是否已经打开并运行

#include <stdio.h>#include <string.h>#include <stdlib.h>#include <unistd.h>#include <sys/socket.h>#include <sys/ioctl.h>#include <net/if.h>#include <sys/types.h>#define IFNAMSIZ 16static int IsIfUp(char *ifname);int c;int main( int argc, char *argv[]){  char *ifname;  int status=0;  if ( argc < 3 )     {        printf("Please input two arguments and try it again!\n");        return 0;     }  while (( c = getopt(argc, argv, "i:")) != -1)        {                switch(c){                case 'i':                        printf("The interface is %s.\n", optarg);                        ifname = optarg;                        break;                case '?':                         printf("Please input two arguments and try it again!\n");                         break;                }        }   if( (status = IsIfUp(ifname)) == 0 )     {     printf("The eth0 status is Up!\n");     return 0;     }  else     {     printf("The eth0 status is down!\n");     return -1;    }  }int IsIfUp(char *ifname){        struct ifreq ifr;        int     sock;        sock = socket(AF_INET, SOCK_DGRAM, 0);        if(sock < 0)        {                perror("socket: Unable to open\n");                return (-1);        }        memcpy(&ifr.ifr_name[0] ,ifname,IFNAMSIZ);          if(ioctl(sock, SIOCGIFFLAGS, &ifr) < 0 )        {                perror("ioctl: SIOCGIFFLAGS");                close(sock);                return (-1);        }        if (!(ifr.ifr_flags & (IFF_UP|IFF_RUNNING)))        {                close(sock);                return (-1);        }        close(sock);          return 0;}