/* This file is part of the sample code and exercises
 * used by the class "Advanced Programming in the UNIX
 * Environment" taught by Jan Schaumann
 * <jschauma@netmeister.org> at Stevens Institute of
 * Technology.
 *
 * This file is in the public domain.
 *
 * You don't have to, but if you feel like
 * acknowledging where you got this code, you may
 * reference me by name, email address, or point
 * people to the course website:
 * https://stevens.netmeister.org/631/
 */

/*
 * World's simplest shell.
 * Loops, reads input and tries to execute it.
 * Note: no tokenization, can be ^C'd, but does look at PATH
 *
 * ./simple-shell
 * $$ ls
 * $$ ls -l # error
 * $$ ^C
 *
 */

#include <sys/types.h>
#include <sys/wait.h>

#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sysexits.h>
#include <unistd.h>

char *
getinput(char *buffer, size_t buflen) {
	printf("$$ ");
	return fgets(buffer, buflen, stdin);
}

int
main(int argc, char **argv) {
	char buf[BUFSIZ];
	pid_t pid;
	int status;

	/* cast to void to silence compiler warnings */
	(void)argc;
	(void)argv;

	while (getinput(buf, sizeof(buf))) {
		buf[strlen(buf) - 1] = '\0';

		if((pid=fork()) == -1) {
			fprintf(stderr, "shell: can't fork: %s\n",
					strerror(errno));
			continue;
		} else if (pid == 0) {   /* child */
			execlp(buf, buf, (char *)0);
			fprintf(stderr, "shell: couldn't exec %s: %s\n", buf,
					strerror(errno));
			exit(EX_UNAVAILABLE);
		}

		/* parent waits */
		if ((pid=waitpid(pid, &status, 0)) < 0) {
			fprintf(stderr, "shell: waitpid error: %s\n",
					strerror(errno));
		}
	}

	exit(EX_OK);
}