Programmatically put display to sleep

display_sleep.cc

#include <CoreFoundation/CoreFoundation.h>
#include <IOKit/IOKitLib.h>

//  clang++ -framework CoreFoundation -framework IOKIT display_sleep.cc

int
main()
{
  const io_registry_entry_t r =
     IORegistryEntryFromPath( kIOMasterPortDefault
                            , "IOService:/IOResources/IODisplayWrangler");
  if (r)
  {
    IORegistryEntrySetCFProperty(r, CFSTR("IORequestIdle"), kCFBooleanTrue);
    IOObjectRelease(r);
    return 0;
  }
  else
  {
    return 1;
  }
}