/*
 * CSE 190, spring 2000.  Created Apr 10, 2000, bsy.
 *
 * Assignment 1.  Run this program interactively.  Observe its
 * behavior.  Run this program with input redirected from a file.
 * Observe its behavior.
 *
 * Based on your observations and -a priori- knowledge of Unix, come
 * up with a theory that explains all that you observed.  Use your
 * theory to predict what would happen if our experiment did not
 * include the first call to fgets(3).
 *
 * Your writeup should include your observations, your theory, and
 * additional candidate experiments to test the various aspects of
 * your theory.  Can these experiments falsify your theory, i.e.,
 * could their outcome force you to abandon or revise your theory?
 */
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <sys/wait.h>

#define	LINESIZE	1024

int	main(void)
{
	char	linebuf[LINESIZE];
	int	pid, status;

	printf("Before fork, please enter a line of text: ");
	if (!fgets(linebuf,sizeof linebuf,stdin)) {
		fprintf(stderr,"Got EOF\n");
		return 1;
	}
	printf("Got(parent,1):\n\"%s\"\n",linebuf);
	switch (pid = fork()) {
	case 0:
		printf("I'm the child.  Please enter another line: ");
		if (!fgets(linebuf,sizeof linebuf,stdin)) {
			fprintf(stderr,"Got EOF child fgets\n");
			return 1;
		}
		printf("Got(child):\n\"%s\"\n",linebuf);
		return 0;
	case -1:
		fprintf(stderr,"fork failed, \"%s\"; errno: %d\n",strerror(errno),errno);
		return 1;
	default:
		printf("I'm the parent of %d; waiting.\n",pid);
		/*
		 * suppose the child returned vital information
		 * as exit status.  is this secure?
		 */
		(void) wait(&status);
		printf("Child exited with status %d\n",status);
		printf("Parent.  Please enter another line of text\n");
		if (!fgets(linebuf,sizeof linebuf,stdin)) {
			fprintf(stderr,"Got EOF parent 2nd fgets\n");
			return 1;
		}
		printf("Got(parent,2):\n\"%s\"\n",linebuf);
	}
	return 0;
}