int result = system(...);
NSString *message, *title;
if (result == 0) {
  title = @"Success!";
  message = @"Operation succeeded.";
} else {
  title =@"Failure!"
  message = [[NSString alloc] initWithFormat:@"Operation failed with error %d!", result];
}

//display message
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:title message:message delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil];
[alert show]
[alert release]