casestuddy1

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

	#define MAX_LINE 4096
	#define MAX_WORDS MAX_LINE/2
	/* a line can have at most MAX_LINE/2 words, why? */
	/* a word is at minimum 2 characters, so the most that can fit in a line is thus MAX/2? */

	void tokenize(char *line, char **words, int *nwords);
	/* break line into words separated by whitespace, placing them in the
	   array words, and setting the count to nwords */

	int system(const char *command);
	int strcmp(const char *str1, const char *str2);
	int externalCommands(const char *command);

	int main()
	{
			char line[MAX_LINE], *words[MAX_WORDS], message[MAX_LINE];
			char linecopy[MAX_LINE];
			int stop=0,nwords=0;

			while(stop==0)
			{
					int i; /* for the for loops */

					printf("OSP CLI $ "); /*this provides the look of a terminal*/

					fgets (line, sizeof(line), stdin);  /* fetches user input for a line */

					/* read a line of text here */

					if (strcmp(line, "")!=0) {
					strcpy(linecopy, line); /* copies the line to linecopy, since tokenizing the line changes it and I'm not sure if we need to keep the original line */
					tokenize(linecopy,words,&nwords); /*tokenizes the line, turning it from a long string into several smaller strings */

					printf("\n input: %s" ,line); /* prints the line, may be removed later if deemed unnecessary */
					} else {
						break;
					}

					for(i=0; i<nwords; i++) {  /* this loop prints the words separately from one another (showing they have been token'd) and also shows the counter */
						printf("word %i = %s \n", i+1, words[i]);
					}

					/* do builtin functions here */

					printf("first word is %s \n", words[0]);

					int isExit;
					int isCd;

					isExit = strcmp(words[0], "exit");
					isCd = strcmp(words[0], "cd");

					if(isExit ==0) {  /* If the user input reads as "exit" then sends a message saying so and terminate the program */
						printf("Exiting program now... \n");
						stop=1; /* setting stop to 1 breaks the while loop */
						break;
					}

					if(isCd==0) { /*This code is if the entered command is "cd", it changes the directory */
							int ret;
							printf("Changing Directory to %s \n", words[1]);
							ret = chdir(words[1]);

							switch (ret) {
								case 0:
									printf("Path successfully changed! \n");
									break;

								case -1:
									printf("Errors in changing directory! \n");
									break;
							}

					}

					/* do external functions with Fork and such */

					/* run an externalCommands(words) */

					if (isExit!=0 && isCd !=0) {
						externalCommands(words[0]);
					}
			}
			return 0;
	}

	/* this function works, it is up to you to work out why! */
	void tokenize(char *line, char **words, int *nwords)
	{
			*nwords=1;

			for(words[0]=strtok(line," \t\n");
				/*Below: if the number of words is below max, and the value at words[nwords] isn't null\n, tokenize the word then add 1 to nwords*/
				/*the function strtok breaks a line into words using a delimiter,  */
				(*nwords<MAX_WORDS)&&(words[*nwords]=strtok(NULL, " \t\n"));
				*nwords=*nwords+1
			   ); /* empty body */
			return;
	}

	int externalCommands(const char *command) {
		pid_t child;
         switch(child=fork())
         {
         case -1:
               perror("fork");
               exit(1);
               break;
         case 0:
               printf("I am the child my pid is: %d\n",getpid());

               exit(0);
               break;
         default:
               printf("I am the parent, my pid is %d," ,getpid());
               printf("and my childs is %d\n",child);
               break;
        }
        return 0;
	}