Get Mac Address of iOS Device.

For iOS

#include <sys/socket.h>

#include <sys/sysctl.h>

#include <net/if.h>

#include <net/if_dl.h>

+ (NSString *)getMacAddress {

 int                 mgmtInfoBase[6];

 char                *msgBuffer = NULL;

  size_t              length;

  unsigned char       macAddress[6];

  
struct if_msghdr    *interfaceMsgStruct;

  struct sockaddr_dl  *socketStruct;

  NSString            *errorFlag = NULL;

  // Setup the management Information Base (mib)

  mgmtInfoBase[0] = CTL_NET;        // Request network subsystem

  mgmtInfoBase[1] = AF_ROUTE;       // Routing table info

  mgmtInfoBase[2] = 0;              

  mgmtInfoBase[3] = AF_LINK;        // Request link layer information

  mgmtInfoBase[4] = NET_RT_IFLIST;  // Request all configured interfaces

  // With all configured interfaces requested, get handle index

  if ((mgmtInfoBase[5] = if_nametoindex("en0")) == 0) 

    errorFlag = @"if_nametoindex failure";

  else

  {

    // Get the size of the data available (store in len)

    if (sysctl(mgmtInfoBase, 6, NULL, &length, NULL, 0) < 0) 

      errorFlag = @"sysctl mgmtInfoBase failure";

    else

    {

      // Alloc memory based on above call

      if ((msgBuffer = malloc(length)) == NULL)

        errorFlag = @"buffer allocation failure";

      else

      {

        // Get system information, store in buffer

        if (sysctl(mgmtInfoBase, 6, msgBuffer, &length, NULL, 0) < 0)

          errorFlag = @"sysctl msgBuffer failure";

      }

    }

  }

  // Befor going any further...

  if (errorFlag != NULL)

  {

    NSLog(@"Error: %@", errorFlag);

    return errorFlag;

  }

  // Map msgbuffer to interface message structure

  interfaceMsgStruct = (struct if_msghdr *) msgBuffer;

  // Map to link-level socket structure

  socketStruct = (struct sockaddr_dl *) (interfaceMsgStruct + 1);

  // Copy link layer address data in socket structure to an array

  memcpy(&macAddress, socketStruct->sdl_data + socketStruct->sdl_nlen, 6);

  // Read from char array into a string object, into traditional Mac address format

  NSString *macAddressString = [NSString stringWithFormat:@"%02X:%02X:%02X:%02X:%02X:%02X", 

                                macAddress[0], macAddress[1], macAddress[2], 

                                macAddress[3], macAddress[4], macAddress[5]];

  NSLog(@"Mac Address: %@", macAddressString);

  // Release the buffer memory

  free(msgBuffer);

  return macAddressString;

}

For Mac OS- 
download sample from
https://developer.apple.com/library/mac/#samplecode/GetPrimaryMACAddress/Introduction/Intro.html