//----------------------------------------------------------------
//	killdemo.cpp
//
//	This program illustrates the use of the 'kill()' library-
//	function, which a process calls in order to send a signal 
//	to another process.  Here our main program forks a child-
//	process which installs a signal-handler, then waits until 
//	it receives a 'SIGUSR1' signal (whereupon it exits).  The
//	parent-process will send the child-process this signal if
//	a user presses the <ENTER>-key. 
//
//	programmer: ALLAN CRUSE
//	written on: 16 SEP 2004
//----------------------------------------------------------------

#include <stdio.h>	// for printf()
#include <signal.h>	// for signal(), kill()
#include <unistd.h>	// for fork()
#include <stdlib.h>	// for exit()
#include <sys/wait.h>	// for wait()


int done = 0;		// global variable


void upon_signal( int intnum )
{
	printf( "signum=%d\n", intnum );
	done = 1;
}	


int main( void )
{
	int	pid = fork();

	if ( pid == 0 ) 
		{ // child-process
		signal( SIGUSR1, upon_signal );
		while ( !done );
		printf( "child is quitting\n\n" );
		}
	else	{ // parent-process
		getchar();
		kill( pid, SIGUSR1 );
		int	status = 0;
		wait( &status );
		printf( "parent is quitting\n\n" );
		}
	exit(0);
}