How to get MAC address of your machine using a C program?

Question

I am working on Ubuntu. How can I get MAC address of my machine or an interface say eth0 using C program.

Answer 1

You need to iterate over all the available interfaces on your machine, and use ioctl with SIOCGIFHWADDR flag to get the mac address. The mac address will be obtained as a 6-octet binary array. You also want to skip the loopback interface.

#include <sys/ioctl.h>
#include <net/if.h> 
#include <unistd.h>
#include <netinet/in.h>
#include <string.h>

int main()
{
    struct ifreq ifr;
    struct ifconf ifc;
    char buf[1024];
    int success = 0;

    int sock = socket(AF_INET, SOCK_DGRAM, IPPROTO_IP);
    if (sock == -1) { /* handle error*/ };

    ifc.ifc_len = sizeof(buf);
    ifc.ifc_buf = buf;
    if (ioctl(sock, SIOCGIFCONF, &ifc) == -1) { /* handle error */ }

    struct ifreq* it = ifc.ifc_req;
    const struct ifreq* const end = it + (ifc.ifc_len / sizeof(struct ifreq));

    for (; it != end; ++it) {
        strcpy(ifr.ifr_name, it->ifr_name);
        if (ioctl(sock, SIOCGIFFLAGS, &ifr) == 0) {
            if (! (ifr.ifr_flags & IFF_LOOPBACK)) { // don't count loopback
                if (ioctl(sock, SIOCGIFHWADDR, &ifr) == 0) {
                    success = 1;
                    break;
                }
            }
        }
        else { /* handle error */ }
    }

    unsigned char mac_address[6];

    if (success) memcpy(mac_address, ifr.ifr_hwaddr.sa_data, 6);
}

Answer 2

Much nicer than all this socket or shell madness is simply using sysfs for this:

the file /sys/class/net/eth0/address carries your mac adress as simple string you can read with fopen()/fscanf()/fclose(). Nothing easier than that.

And if you want to support other network interfaces than eth0 (and you probably want), then simply use opendir()/readdir()/closedir() on /sys/class/net/.

Answer 3

You want to take a look at the getifaddrs(3) manual page. There is an example in C in the manpage itself that you can use. You want to get the address with the type AF_LINK.

Answer 4

#include <sys/socket.h>
#include <sys/ioctl.h>
#include <linux/if.h>
#include <netdb.h>
#include <stdio.h>
#include <string.h>

int main()
{
  struct ifreq s;
  int fd = socket(PF_INET, SOCK_DGRAM, IPPROTO_IP);

  strcpy(s.ifr_name, "eth0");
  if (0 == ioctl(fd, SIOCGIFHWADDR, &s)) {
    int i;
    for (i = 0; i < 6; ++i)
      printf(" %02x", (unsigned char) s.ifr_addr.sa_data[i]);
    puts("\n");
    return 0;
  }
  return 1;
}

Answer 5

Using getifaddrs you can get MAC address from the family AF_PACKET.

In order to display the MAC address to each interface, you can proceed like this:

#include <stdio.h>
#include <ifaddrs.h>
#include <netpacket/packet.h>

int main (int argc, const char * argv[])
{
    struct ifaddrs *ifaddr=NULL;
    struct ifaddrs *ifa = NULL;
    int i = 0;

    if (getifaddrs(&ifaddr) == -1)
    {
         perror("getifaddrs");
    }
    else
    {
         for ( ifa = ifaddr; ifa != NULL; ifa = ifa->ifa_next)
         {
             if ( (ifa->ifa_addr) && (ifa->ifa_addr->sa_family == AF_PACKET) )
             {
                  struct sockaddr_ll *s = (struct sockaddr_ll*)ifa->ifa_addr;
                  printf("%-8s ", ifa->ifa_name);
                  for (i=0; i <s->sll_halen; i++)
                  {
                      printf("%02x%c", (s->sll_addr[i]), (i+1!=s->sll_halen)?':':'\n');
                  }
             }
         }
         freeifaddrs(ifaddr);
    }
    return 0;
}

Ideone

Answer 6

I have just write one and test it on gentoo in virtualbox.

// get_mac.c
#include <stdio.h>    //printf
#include <string.h>   //strncpy
#include <sys/socket.h>
#include <sys/ioctl.h>
#include <net/if.h>   //ifreq
#include <unistd.h>   //close

int main()
{
    int fd;
    struct ifreq ifr;
    char *iface = "enp0s3";
    unsigned char *mac = NULL;

    memset(&ifr, 0, sizeof(ifr));

    fd = socket(AF_INET, SOCK_DGRAM, 0);

    ifr.ifr_addr.sa_family = AF_INET;
    strncpy(ifr.ifr_name , iface , IFNAMSIZ-1);

    if (0 == ioctl(fd, SIOCGIFHWADDR, &ifr)) {
        mac = (unsigned char *)ifr.ifr_hwaddr.sa_data;

        //display mac address
        printf("Mac : %.2X:%.2X:%.2X:%.2X:%.2X:%.2X\n" , mac[0], mac[1], mac[2], mac[3], mac[4], mac[5]);
    }

    close(fd);

    return 0;
}

Answer 7

Assuming that c++ code (c++11) is ok as well and the interface is known.

#include <cstdint>
#include <fstream>
#include <streambuf>
#include <regex>

using namespace std;

uint64_t getIFMAC(const string &ifname) {
  ifstream iface("/sys/class/net/"+ifname+"/address");
  string str((istreambuf_iterator<char>(iface)), istreambuf_iterator<char>());
  if (str.length() > 0) {
    string hex = regex_replace(str, std::regex(":"), "");
    return stoull(hex, 0, 16);
  } else {
    return 0;
  }
} 
int main()
{
  string iface="eth0";
  printf("%s: mac=%016lX\n", iface.c_str(), getIFMAC(iface));
}

Answer 8

1. On Linux, use the service of "Network Manager" over the DBus.

2. There is also good'ol shell program which can be invoke and the result grabbed (use an exec function under C):

$ /sbin/ifconfig | grep HWaddr

Answer 9

A very portable way is to parse the output of this command.

ifconfig | awk '$0 ~ /HWaddr/ { print $5 }'

Provided ifconfig can be run as the current user (usually can) and awk is installed (it often is). This will give you the mac address of the machine.

Answer 10

This is a Bash line that prints all available mac addresses, except the loopback:

for x in `ls /sys/class/net |grep -v lo`; do cat /sys/class/net/$x/address; done

Can be executed from a C program.

Answer 11

Expanding on the answer given by @user175104 ...

std::vector<std::string> GetAllFiles(const std::string& folder, bool recursive = false)
{
  // uses opendir, readdir, and struct dirent.
  // left as an exercise to the reader, as it isn't the point of this OP and answer.
}

bool ReadFileContents(const std::string& folder, const std::string& fname, std::string& contents)
{
  // uses ifstream to read entire contents
  // left as an exercise to the reader, as it isn't the point of this OP and answer.
}

std::vector<std::string> GetAllMacAddresses()
{
  std::vector<std::string> macs;
  std::string address;

  // from: https://stackoverflow.com/questions/9034575/c-c-linux-mac-address-of-all-interfaces
  //  ... just read /sys/class/net/eth0/address

  // NOTE: there may be more than one: /sys/class/net/*/address
  //  (1) so walk /sys/class/net/* to find the names to read the address of.

  std::vector<std::string> nets = GetAllFiles("/sys/class/net/", false);
  for (auto it = nets.begin(); it != nets.end(); ++it)
  {
    // we don't care about the local loopback interface
    if (0 == strcmp((*it).substr(-3).c_str(), "/lo"))
      continue;
    address.clear();
    if (ReadFileContents(*it, "address", address))
    {
      if (!address.empty())
      {
        macs.push_back(address);
      }
    }
  }
  return macs;
}