/*   * main.c   * ----------------------------------------------   * 2013-01-09 chrisniu1984@gmail.com   *   * [BUILD]   * gcc -o main main.c -Wall   *   */     #include <stdio.h>     #include <netdb.h>  #include <ifaddrs.h>     // 系统定义的结构，贴在这里方便大家查阅，也可man getifaddrs查看。  // struct ifaddrs {  //     struct ifaddrs  *ifa_next;    /* Next item in list */  //     char            *ifa_name;    /* Name of interface */  //     unsigned int     ifa_flags;   /* Flags from SIOCGIFFLAGS */  //     struct sockaddr *ifa_addr;    /* Address of interface */  //     struct sockaddr *ifa_netmask; /* Netmask of interface */  //     union {  //         struct sockaddr *ifu_broadaddr;  //                          /* Broadcast address of interface */  //         struct sockaddr *ifu_dstaddr;  //                          /* Point-to-point destination address */  //     } ifa_ifu;  // #define              ifa_broadaddr ifa_ifu.ifu_broadaddr  // #define              ifa_dstaddr   ifa_ifu.ifu_dstaddr  //     void            *ifa_data;    /* Address-specific data */  // };     int main(int argc, char **argv)  {      struct ifaddrs *ifa;      if (getifaddrs(&ifa) != 0) {          return -1;      }             for (; ifa!=NULL; ifa=ifa->ifa_next) {          struct sockaddr_in *sin = (struct sockaddr_in*)ifa->ifa_addr;          if (sin->sin_family != AF_INET) {              continue;          }             unsigned char *b = (unsigned char *)(&sin->sin_addr.s_addr);          printf("%s\t%u.%u.%u.%u\n", ifa->ifa_name, b[0], b[1], b[2], b[3]);      }         return 0;  }