How to programmatically prevent a Mac from going to sleep?

Question

Is there way to prevent a Mac from going to sleep programmatically using Objective-C? The I/O kit fundamentals section on Apple's dev site tells me that a driver gets notified of an idle / system sleep, but I can't find a way of preventing the system from sleeping. Is it even possible?

I've come across some other solutions using Caffeine, jiggler, sleepless and even AppleScript, but I want to do this in Objective-C. Thanks.

Answer 1

Here is the official Apple documentation (including code snippet):
Technical Q&A QA1340 - How to I prevent sleep?

Quote: Preventing sleep using I/O Kit in Mac OS X 10.6 Snow Leopard:

#import <IOKit/pwr_mgt/IOPMLib.h>  // kIOPMAssertionTypeNoDisplaySleep prevents display sleep, // kIOPMAssertionTypeNoIdleSleep prevents idle sleep  // reasonForActivity is a descriptive string used by the system whenever it needs  // to tell the user why the system is not sleeping. For example,  // "Mail Compacting Mailboxes" would be a useful string.  // NOTE: IOPMAssertionCreateWithName limits the string to 128 characters.  CFStringRef* reasonForActivity= CFSTR("Describe Activity Type");  IOPMAssertionID assertionID; IOReturn success = IOPMAssertionCreateWithName(kIOPMAssertionTypeNoDisplaySleep,                                      kIOPMAssertionLevelOn, reasonForActivity, &assertionID);  if (success == kIOReturnSuccess) {     //  Add the work you need to do without      //  the system sleeping here.      success = IOPMAssertionRelease(assertionID);     //  The system will be able to sleep again.  } 

For older OSX version, check the following:
Technical Q&A QA1160 - How can I prevent system sleep while my application is running?

Quote: Example usage of UpdateSystemActivity (the canonical way for < 10.6)

#include <CoreServices/CoreServices.h>  void MyTimerCallback(CFRunLoopTimerRef timer, void *info) {     UpdateSystemActivity(OverallAct); }   int main (int argc, const char * argv[]) {     CFRunLoopTimerRef timer;     CFRunLoopTimerContext context = { 0, NULL, NULL, NULL, NULL };      timer = CFRunLoopTimerCreate(NULL, CFAbsoluteTimeGetCurrent(), 30, 0, 0, MyTimerCallback, &context);     if (timer != NULL) {         CFRunLoopAddTimer(CFRunLoopGetCurrent(), timer, kCFRunLoopCommonModes);     }      /* Start the run loop to receive timer callbacks. You don't need to     call this if you already have a Carbon or Cocoa EventLoop running. */     CFRunLoopRun();      CFRunLoopTimerInvalidate(timer);     CFRelease(timer);      return (0); }