Thanks for the hints guys. I've split it up and get more response now. When running the command without backslashes & without the sort & head I do get results.
NSArray *args = @[@".",
@"!",
@"-path",
@"*.git*",
@"-exec",
@"stat",
@"-f",
@"%m",
@"{}",
@";"];
So it looks like NSTask should not be fed '|' characters. I'll just so the sorting etc. in objc.