/**********************************************************
 *
 *	badpingpong.c
 *
 *	Started by Jeff Ondich on 4/25/02
 *	Last modified on 4/26/02
 *
 *	For exam due 5/3/02.
 *	This program tries to send signals alternately
 *	between parent and child, but it has a problem.
 *
 **********************************************************/

#include	<sys/types.h>
#include	<sys/wait.h>
#include	<unistd.h>
#include	<stdlib.h>
#include	<stdio.h>


void parent_handler();
void child_handler();
void interrupt_handler();

int main( void )
{
	int			pid;

	if( signal(SIGINT,interrupt_handler) != SIG_DFL )
		fprintf( stderr, "Trouble setting SIGINT handler.\n" );


	/* Fork */
	pid = fork();
	if( pid == -1 )
	{
		perror( "fork() failure" );
	}

	/* Parent */
	else if( pid != 0 )
	{
		if( signal(SIGUSR1,parent_handler) != SIG_DFL )
			fprintf( stderr, "Trouble setting parent's signal handler.\n" );

		while( 1 )
		{
			pause();
			kill( pid, SIGUSR1 );
		}
	}

	/* Child */
	else
	{
		fprintf( stderr, "Child\n" );
		fflush( stderr );
		if( signal(SIGUSR1,child_handler) != SIG_DFL )
			fprintf( stderr, "Trouble setting child's signal handler.\n" );

		fprintf( stderr, "Child2\n" );
		fflush( stderr );
		while( 1 )
		{
			kill( getppid(), SIGUSR1 );
			pause();
		}
	}

	return 0;
}

void interrupt_handler( int sig )
{
	exit( 0 );
}

void parent_handler( int sig )
{
	fprintf( stderr, "PONG.  Parent got signal %d from child.\n", sig );
}

void child_handler( int sig )
{
	fprintf( stderr, "PING.  Child got signal %d from parent\n", sig );
}