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

#define MAXARGS 128
#define MAXLINE 80
#define FOREVER while(1)

extern char **environ;

void eval(char *cmdline);
int parseline(char *buf, char **argv);
int builtin_cmd(char **argv);

int main() {
	char cmdline[MAXLINE];
	
	FOREVER {
		printf("> ");
		fgets(cmdline, MAXLINE, stdin);
		if (feof(stdin)) exit(0);
		
		eval(cmdline);
	}
		return EXIT_SUCCESS;
}


void eval(char *cmdline) {
	char *argv[MAXARGS];
	char buf[MAXLINE];
	int bg;
	pid_t pid;
	
	strcpy(buf, cmdline);
	bg = parseline(buf, argv);
	if (argv[0] == NULL) {
		return;
	}
	
	if (!builtin_cmd(argv)) {
		if ((pid = fork()) == 0) {
			if (execvp(argv[0], argv) < 0) {
				printf("%s: cette commande n'existe pas.\n", argv[0]);
				exit(0);
			}
		}
		
		if (!bg) {
			int status;
			if (waitpid(pid, &status, 0) < 0) {
				perror("waitfg: waitpid error"); exit(0);
			}
		}
		else {
			printf("%d %s", pid, cmdline);
		}
	}
	return;
}

int builtin_cmd(char **argv) {
	if (!strcmp(argv[0], "quit"))
		exit(0);
	if (!strcmp(argv[0], "&"))
		return 1;
	return 0;
}

int parseline(char *buf, char **argv) {
	char *delim;
	int argc;
	int bg; 
	
	buf[strlen(buf)-1] = ' ';
	while (*buf && (*buf == ' ')) {
		buf++;
	}
	
	argc = 0;
	while ((delim = strchr(buf, ' '))) {
		argv[argc++] = buf;
		*delim = '\0';
		buf = delim+1;
		while (*buf && (*buf == ' ')) buf++;
	}
	argv[argc] = NULL;
	
	if (argc == 0) return 1;
	
	if ((bg = (*argv[argc-1] == '&')) != 0) {
		argv[--argc] = NULL;
	}
	
	return bg;	
}