Check for device iOS version. is device is iOS 5 or iOS 6.

+ (BOOL) isIOS5

{

    NSString *os5 = @"5.0";

    NSString *currSysVer = [[UIDevice currentDevice] systemVersion];

    

    //    currSysVer = @"5.0.1";

    if ([currSysVer compare:os5 options:NSNumericSearch] == NSOrderedAscending) //lower than 4

    {

        return NO;

    }

    else if ([currSysVer compare:os5 options:NSNumericSearch] == NSOrderedDescending) //5.0.1 and above

    {

        return YES;

    }

    else // IOS 5

    {

        return YES;

    }

    

    return NO;

}

+ (BOOL) isIOS6

{

    NSString *os6 = @"6.0";

    NSString *currSysVer = [[UIDevice currentDevice] systemVersion];

    

    //    currSysVer = @"6.0.1";

    if ([currSysVer compare:os6 options:NSNumericSearch] == NSOrderedAscending)

    {

        return NO;

    }

    else if ([currSysVer compare:os6 options:NSNumericSearch] == NSOrderedDescending)

    {

        return YES;

    }

    else // IOS 5

    {

        return YES;

    }

    

    return NO;

}

Check if iOS current device is having retina display?

#pragma mark- Device Check=

+ (BOOL) isRetina

{

    if([[UIScreen mainScreen] respondsToSelector:@selector(scale)])

        return [[UIScreen mainScreen] scale] == 2.0 ? YES : NO;

    

    return NO;

}

Check if multitasking is available iOS device?

#pragma mark- Multitasking -

+(BOOL)multitaskingAvailable

{

UIDevice* device = [UIDevice currentDevice];

BOOL backgroundIsSupported = NO;

if ([device respondsToSelector:@selector(isMultitaskingSupported)])

   backgroundIsSupported = device.multitaskingSupported;

return backgroundIsSupported;

}

Redirect NSLog to file.

#pragma mark- Redirect NSLog to file-

+ (void)redirectNSLogToDocumentFolder

{

    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,NSUserDomainMask, YES);

    

    NSString *documentsDirectory = [paths objectAtIndex:0];

    

    NSString *fileName =[NSString stringWithFormat:@"NSLogFile"];

    

    NSString *logFilePath = [documentsDirectory stringByAppendingPathComponent:fileName];

    

    NSLog(@"Redirecting NSLog to file");

    freopen([logFilePath cStringUsingEncoding:NSASCIIStringEncoding],"a+",stderr);

    

}

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