Get IPv4 Address Programatically

README.md

Get IPv4 Address Programatically

For more detail info: https://amarullz.com/2022/05/18/linux-c-fungsi-untuk-mengetahui-ip-address-secara-program/

License

Copyright 2022 Ahmad Amarullah (https://amarullz.com)

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

get_ipv4address.c

/*
 * Copyright 2022 Ahmad Amarullah (https://amarullz.com)
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 * 
 */

#include <arpa/inet.h>
#include <sys/socket.h>
#include <netdb.h>
#include <ifaddrs.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>

/**
 * Dapatkan ip address untuk interface tertentu
 *
 * @param const char * nama interface (eth0, wlan0, lo)
 * @param char * output buffer untuk menampung ip address
 * @param int ukuran buffer
 * @return int Bila berhasil berisi panjang output. 0 bila gagal
 */
int get_ipv4address(const char* iface, char* out, int sz) {
  // Pastikan output buffer tidak null
  if (!out) return 0;

  struct ifaddrs *ifaddr, *ifa;
  char host[NI_MAXHOST];
  int len = 0;

  // Ambil semua alamat interface
  if (getifaddrs(&ifaddr) == -1) return 0;

  // Loop untuk mencari interface yang dicari
  for (ifa = ifaddr; ifa != NULL; ifa = ifa->ifa_next) {
    if (ifa->ifa_addr == NULL) continue;

    // Cek kecocokan string
    if ((strcmp(ifa->ifa_name, iface) == 0) &&
        (ifa->ifa_addr->sa_family == AF_INET)) {
      // Copy ip address kedalam variabel
      if (getnameinfo(ifa->ifa_addr, sizeof(struct sockaddr_in), host,
                      NI_MAXHOST, NULL, 0, NI_NUMERICHOST) != 0)
        return 0;

      // Simpan ip address pada output buffer
      len = snprintf(out, sz, "%s", host);
      // Break agar tidak perlu mencari yang lain
      break;
    }
  }

  // Free linked list interface
  freeifaddrs(ifaddr);
  return len;
}

// Contoh cara penggunaan
int main(int argc, char *argv[]){
  char ip[16];
  if (get_ipv4address("eth0", ip, 16)>0)
    printf("IP Address untuk eth0 adalah: %s\n",ip);
  else
    printf("IP Address tidak ditemukan\n");
  return 0;
}