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

User · Answer

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

User · Answer

Assuming that c   code  c  11  is okay as well and the interface is known   include  lt cstdint gt   include  lt fstream gt   include  lt streambuf gt   include  lt regex gt   using namespace std   uint64 t getIFMAC const string  amp ifname      ifstream iface  quot  sys class net  quot    ifname    quot  address quot      string str  istreambuf iterator lt char gt  iface    istreambuf iterator lt char gt        if  str length    gt  0        string hex   regex replace str  std  regex  quot   quot     quot  quot        return stoull hex  0  16       else       return 0         int main       string iface    quot eth0 quot     printf  quot  s  mac  016llX n quot   iface c str    getIFMAC iface

User · Answer

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  lt sys ioctl h gt   include  lt net if h gt    include  lt unistd h gt   include  lt netinet in h gt   include  lt string h gt   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   amp 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- gt ifr name           if  ioctl sock  SIOCGIFFLAGS   amp ifr     0                if     ifr ifr flags  amp  IFF LOOPBACK        don t count loopback                 if  ioctl sock  SIOCGIFHWADDR   amp ifr     0                        success   1                      break                                                    else      handle error                 unsigned char mac address 6        if  success  memcpy mac address  ifr ifr hwaddr sa data  6

User · Answer

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

User · Answer

Expanding on the answer given by  user175104      std  vector lt std  string gt  GetAllFiles const std  string amp  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 amp  folder  const std  string amp  fname  std  string amp  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 lt std  string gt  GetAllMacAddresses       std  vector lt std  string gt  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 lt std  string gt  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

User · Answer

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

User · Answer

netlink socket is possible man netlink 7  netlink 3  rtnetlink 7  rtnetlink 3   include  lt assert h gt   include  lt stdio h gt   include  lt linux if h gt   include  lt linux rtnetlink h gt   include  lt unistd h gt    define SZ 8192  int main          Send   typedef struct       struct nlmsghdr nh      struct ifinfomsg ifi      Req getlink    assert NLMSG LENGTH sizeof struct ifinfomsg    sizeof Req getlink      int fd -1    fd socket AF NETLINK SOCK RAW NETLINK ROUTE     assert 0  bind fd  struct sockaddr    amp  struct sockaddr nl        nl family AF NETLINK       nl pad 0       nl pid getpid         nl groups 0      sizeof struct sockaddr nl       assert sizeof Req getlink   send fd  amp  Req getlink        nh          nlmsg len NLMSG LENGTH sizeof struct ifinfomsg           nlmsg type RTM GETLINK         nlmsg flags NLM F REQUEST NLM F ROOT         nlmsg seq 0         nlmsg pid 0             ifi          ifi family AF UNSPEC            ifi family AF INET         ifi type 0         ifi index 0         ifi flags 0         ifi change 0            sizeof Req getlink  0          Receive   char recvbuf SZ        int len 0    for char  p recvbuf         const int seglen recv fd p sizeof recvbuf -len 0       assert seglen gt  1       len    seglen      if   struct nlmsghdr  p - gt nlmsg type  NLMSG DONE    struct nlmsghdr  p - gt nlmsg type  NLMSG ERROR        break      p    seglen         struct nlmsghdr  nh  struct nlmsghdr  recvbuf    for  NLMSG OK nh len  nh NLMSG NEXT nh len        if nh- gt nlmsg type  NLMSG DONE        break       struct ifinfomsg  ifm  struct ifinfomsg  NLMSG DATA nh        printf  quot   d  quot  ifm- gt ifi index        ifdef  NET IF H      pragma GCC error  quot include  lt linux if h gt  instead of  lt net if h gt  quot       endif         Part 3 rtattr     struct rtattr  rta IFLA RTA ifm       usr include linux if link h     int rtl RTM PAYLOAD nh        for  RTA OK rta rtl  rta RTA NEXT rta rtl  switch rta- gt rta type       case IFLA IFNAME printf  quot  s  quot   const char  RTA DATA rta   break      case IFLA ADDRESS        printf  quot hwaddr  quot          for int i 0 i lt 5   i          printf  quot  02X  quot     unsigned char  RTA DATA rta  i          printf  quot  02X  quot     unsigned char  RTA DATA rta  5          break      case IFLA BROADCAST        printf  quot bcast  quot          for int i 0 i lt 5   i          printf  quot  02X  quot     unsigned char  RTA DATA rta  i          printf  quot  02X  quot     unsigned char  RTA DATA rta  5          break      case IFLA PERM ADDRESS        printf  quot perm  quot          for int i 0 i lt 5   i          printf  quot  02X  quot     unsigned char  RTA DATA rta  i          printf  quot  02X  quot     unsigned char  RTA DATA rta  5          break             printf  quot  n quot            close fd     fd -1    return 0       Example  1 lo hwaddr 00 00 00 00 00 00 bcast 00 00 00 00 00 00  2 eth0 hwaddr 57 da 52 45 5b 1a bcast ff ff ff ff ff ff perm 57 da 52 45 5b 1a  3 wlan0 hwaddr 3c 7f 46 47 58 c2 bcast ff ff ff ff ff ff perm 3c 7f 46 47 58 c2

User · Answer

include  lt sys socket h gt   include  lt sys ioctl h gt   include  lt linux if h gt   include  lt netdb h gt   include  lt stdio h gt   include  lt string h gt   int main       struct ifreq s    int fd   socket PF INET  SOCK DGRAM  IPPROTO IP      strcpy s ifr name   eth0      if  0    ioctl fd  SIOCGIFHWADDR   amp s         int i      for  i   0  i  lt  6    i        printf    02x    unsigned char  s ifr addr sa data i        puts   n        return 0        return 1

User · Answer

On Linux  use the service of  Network Manager  over the DBus  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

User · Answer

I have just write one and test it on gentoo in virtualbox      get mac c  include  lt stdio h gt       printf  include  lt string h gt      strncpy  include  lt sys socket h gt   include  lt sys ioctl h gt   include  lt net if h gt      ifreq  include  lt unistd h gt      close  int main         int fd      struct ifreq ifr      char  iface    enp0s3       unsigned char  mac   NULL       memset  amp 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   amp 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

User · Answer

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

User · Answer

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

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

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