#include 
     
       #include 
      
        FILE *fp = NULL; #define NETWORK_FILE "/etc/network/interfaces" static char* getNetworkInfo(char *maches) {
   char szBuf[64]; char *szNetwork=NULL; int i = 0; if((fp=fopen(NETWORK_FILE, "r"))==NULL)             //判断文件是否为空     {
           printf( "Can 't   open   file!\n"); return 0;     } while(fgets(szBuf,128,fp))                         //从文件开关开始向下读，把读到的内容放到szBuf中     {                         if(strstr(szBuf,maches) != NULL)                 //找到maches在文件中第一次出现的位置。。如address         {
   for(i =0;i < strlen(szBuf);i++)           {              if(isdigit(*(szBuf+i)))                      //从szBuf字符串中找出数字。                 {
                       szNetwork = (char*)malloc(strlen(szBuf));  //为szNetwork分配内存                     strcpy(szNetwork,szBuf+i);                                 szNetwork[strlen(szNetwork)-1] = '\0';                     fclose(fp); return szNetwork;                 }             }         }else continue;     }     fclose(fp); return szNetwork; } int main() {
   char *IPaddress; char *netmask; char *gateway;     IPaddress = getNetworkInfo("address");               //找到 LINUX 配制文件中的 interfaces 文件 匹配IP 。然后读出来     netmask   = getNetworkInfo("netmask");               //子网掩码     gateway   = getNetworkInfo("gateway");               //默认网关     printf("IPaddress:%s\n",IPaddress);     printf("netmask:%s\n",netmask);     printf("gateway:%s\n",gateway); } /*****************************  *    interfaces 里的内容    *  *                           * *****************************/ /***************************** iface lo inet loopback                      auto eth0 iface eth0 inet static         address 192.168.1.139         netmask 255.255.255.0         gateway 192.168.1.1 *****************************/
      
     

static void writeAddr(char addressbuf[255])                 //IP 写入 {
        FILE* fp=NULL; int i,Lid = -1; char szBuf[128]; char szTemp[128]; char szTmp[20][256];   memset(szTmp,0,sizeof(szTmp));   memset(szBuf,0,sizeof(szBuf)); if((fp=fopen(NETWORK_FILE, "r+"))==NULL)     {         printf( "setIP Can 't open file!\n"); return;     } while(fgets(szBuf,256,fp))     {
            Lid++; if('#' != *szBuf)         {
    if(strstr(szBuf,"gateway") != NULL)             {
                    memset(szTemp,0,sizeof(szTemp));                 snprintf(szTemp, sizeof(szTemp), "\tgateway %s\n",addressbuf);                 strcpy(szTmp[Lid],szTemp);             }else                 strcpy(szTmp[Lid],szBuf);         }else{
                strcpy(szTmp[Lid],szBuf);         }     }     fclose(fp);     printf("%s\n",szTmp[6]); if((fp=fopen(NETWORK_FILE, "w"))==NULL)     {         printf( "writeIP Can 't open file!\n"); return;     }else{
    for(i = 0;i <=Lid;i++)             fputs(szTmp[i],fp);         fclose(fp);     } return; }