get the file extension of given file

hi,
    Considered as the tamil.txt file there in document folder. You want to get the file extension.
Step 1:
         First you need to get the document folder path using below code

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

NSString *documentDirectory = [paths objectAtIndex:0];

Step 2:

      Then you need to get the exact file name path

 NSString *path=[documentDirectory stringByAppendPathComponent:@"tamil.txt"];

Step 3:

      Now you knew the exact path of file name.

then,

     NSString *fileExtension=[path pathExtension];

NSLog(@"file extension ==%@", fileExtension);