sleep1.c

understanding unix/linux programming source code(bruce molay)

/* sleep1.c
 *	purpose	show how sleep works
 *	usage	sleep1
 *	outline	sets handler, sets alarm, pauses, then returns
 */
#include	<stdio.h>
#include	<signal.h>
// #define	SHHHH

main()
{
	void	wakeup(int);

	printf("about to sleep for 4 seconds\n");
	signal(SIGALRM, wakeup);		/* catch it	*/
	alarm(4);				/* set clock	*/
	pause();				/* freeze here	*/
	printf("Morning so soon?\n");		/* back to work	*/
}

void wakeup(int signum)
{
#ifndef SHHHH
	printf("Alarm received from kernel\n");
#endif
}