shell

// Modify this file for your assignment
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <signal.h> //for command signal to exit
#define MAX_INPUT_SIZE 80
#include <sys/types.h>
#include <sys/wait.h>

char input [81];
	
void initialize_shell(){

	system("clear"); //clear the current screen
	printf("\n\n\n*******************************************************************");
	printf("\n\n\t\tWelcome to Mariah's shell");
	printf("\n\n\n*******************************************************************");



}

void help(){
	printf("WELCOME to Mariah's terminal.The following built in commands are supported.\n");
	printf("cd -- displays current location in the directory\n");
	printf("exit -- will close the current terminal\n");
	printf("help -- displays all the available built-in commands\n");
	printf("history -- this command will print all previous user input\n");


}


void term_commands(char** array, int* p){

	pid_t pid = fork(); //create child process
	int status;

	if(pid == 0){ //child process
		execvp(array[0],array); //perform command

		exit(1);		
	}

	else{	
		wait(NULL); //wait for child process to execute
		
	}
	

}


void sigint_handler(int sig){

	write(1,"Mini-shell terminated\n",22);
	exit(0);


}

void print_history(char** hist, int count){
	int i;
	for(i=0; i<count;i++){ //loop through array
		printf(" %s\n",hist[i]); //print each array element (command)
	}	


}

void add_history(char* string, int count,char** hist){
	hist[count] = strdup(string);

}
void builtin_commands(char* command, char** array, char** hist, int count){

	if(strcmp(command,"help")==0){
		
		help(); //go to help function
	}
	else if(strcmp(command,"history")==0){
		
		print_history(hist,count); //print history array
	}
	else if(strcmp(command,"cd")==0){
		
		chdir(array[1]); //change directory
	}


}


void read_pipe(char** command1, char** command2){
	
	int fd[2];
	pipe(fd);
	//beginning pipe processing now..
	int pid1 = fork();

	if(pid1 ==0) { //child process
	dup2(fd[1],STDOUT_FILENO); //write end of the pipe is fd1
	close(fd[0]);
	close(fd[1]);
	//call execvp function here
	execvp(command1[0],command1); //perform command
	exit(1);

	}
	waitpid(pid1,NULL,0);

	int pid2 = fork();

	if(pid2==0){ //child
	dup2(fd[0], STDIN_FILENO);
	close(fd[0]);
	close(fd[1]);
	//write execvp function here
	execvp(command2[0],command2);
	exit(1);	
	
	}
	close(fd[0]);
	close(fd[1]);
	waitpid(pid2,NULL,0);

	
}


void command_type(char input[],char** parsed_tok,char** _history, int count){

	int flag = 0;//flag will change if command is supported within mini shell
	int flag2 = 0;
	char* builtin [] = {"help","history","cd"};

	char* command;
	command = parsed_tok[0]; //looking at first command word
	int i;	


	//Checking the type of command now..	


	//checking if builtin
	for(i=0;i<3;i++){
		if(strcmp(command,builtin[i]) == 0){ //checking for builtin command

			builtin_commands(builtin[i],parsed_tok,_history,count);			
			break;
		}

	}
	

	//checking if terminal command
	term_commands(parsed_tok,&flag2);

}

void parse_commands(char input[],int count,char** _history){

	add_history(input,count,_history);	

	char* parsed_tok[80]; //array of 80 strings
	char* parsed_tok2[80]; //holds strings after pipe
	char* token = strtok(input, " ");
	
	int pipe_found=0;	
	int i = 0;		
	int j = 0; //counter for number of tokens
	while(token != NULL){ //splitting input into strings
		if(strcmp(token,"|")==0){ //checking for pipe operator in command
			token = strtok(NULL, " "); //if found, token is saved and while loop broken
			pipe_found = 1;
			break;
		}
		parsed_tok[i++] = token;

		j++;
		token = strtok(NULL, " ");
		
		}
	
	parsed_tok[i] = NULL;
	
	if(pipe_found ==1){
		i = 0;
		while(token !=NULL){ //store right command of pipe
			parsed_tok2[i++] = token;
			token = strtok(NULL," ");	
		
		}
	parsed_tok2[i] = NULL;
	}

	if(pipe_found ==1){ //pipe reading function
		read_pipe(parsed_tok,parsed_tok2);
	}
	else{ 
	command_type(input,parsed_tok,_history,count);

	}
}


int main(){
  alarm(180); // Please leave in this line as the first statement in your program.
              // This will terminate your shell after 180 seconds,
              // and is useful in the case that you accidently create a 'fork bomb'
  
	signal(SIGINT, sigint_handler);

	initialize_shell();

	
	printf("\nYou can only terminate by pressing Ctrl+c\n");
	
	char** _history = (char**)malloc(sizeof(char*) * 80);
	int count = 0; //track number of commands for history array
	while(1){ //will run forever
		char* inputp;

		printf("mini-shell>");

		inputp = fgets(input,MAX_INPUT_SIZE,stdin); //getting user input & storing in array
		input[strlen(input)-1] = '\0'; //removing null character at end of string
		
		if(strcmp(input,"exit")==0){ //checking if user wants to exit
			int i;
			for(i=0; i<count;i++){ //loop through array
				free(_history[i]); //print each array element (command)
			}	
			free(_history);
			exit(0);
	
		}

		else{
		parse_commands(input,count,_history);
		count++; 
		sleep(1);
		}
	



	}

  return 0;

}