#include	<stdio.h>

#define	oops(m)	{ perror(m); exit(1); }

main()
{
	int	p[2];

	pipe(p);

	if ( fork() == 0 )
		child(p);
	parent(p);
}

/*
 * child waits for parent message
 */
child(int p[])
{
	char	x[100];
	int	n;
	int	k = 0;

	while(1)
	{	
		n = read(p[0], x, 100);
		if ( n == -1 )
			oops("read in child");
		write(1,"child: ",7);
		write(1, x, n);

		sprintf(x, "from child %d\n", k++);
		if ( write(p[0], x, strlen(x)) == -1 )
			oops("write from child");
	}
}
/*
 * parent writes first message
 */
parent(int p[])
{
	char	x[100];
	int	n;
	int	k = 0;

	while(1)
	{	
		sprintf(x, "from parent %d\n", k++);
		if ( write(p[1], x, strlen(x)) == -1 )
			oops("write from parent");

		n = read(p[1], x, 100);
		if ( n == -1 )
			oops("read in parent");
		write(1,"parent: ",9);
		write(1, x, n);

	}
}