Lab2_sandeep-2.tar

HW2/0000755003432100136040000000000013547516627011421 5ustar  singh96studentsHW2/Makefile0000644003432100136040000000003513545446416013053 0ustar  singh96studentshw2: hw2.c
	gcc -o hw2 hw2.c
HW2/hw2.c0000644003432100136040000001455613547516530012271 0ustar  singh96students#include <stdio.h>

#include<stdlib.h>

#include <string.h>

#include <stdbool.h>
#include <fcntl.h>
#include <sys/wait.h>
#include <unistd.h>
void deploy(char **no_of_arg,char inputfile[],char outputfile[])
{
    int copy2, copy1, i;
  int pipefd[2];
  

  i = pipe(pipefd);
  if (i < 0) {
    perror("pipe"); exit(1);
  }


  if (fork() == 0) {
     
     
    //First child:
    if (dup2(pipefd[1], 1) != 1) {
      perror("dup2");
      exit(1);
    }    
    close(pipefd[1]);
    close(pipefd[0]);
    if(strcmp(inputfile,"None")!=0)
    {
    pipefd[0] = open(inputfile, O_CREAT | O_WRONLY | O_TRUNC, 0644);
    }
    if(execvp(*no_of_arg, no_of_arg) < 0 ) {
      perror("execvp");
    }
  } else if (fork() == 0) {
      
        
    //Second child:
    if (dup2(pipefd[0], 0) != 0) {   
      perror("dup2");
      exit(1);
    }   
    close(pipefd[1]);
    close(pipefd[0]);
    if(strcmp(outputfile,"None")!=0)
    {
    pipefd[1]=open(outputfile, O_WRONLY | O_TRUNC | O_CREAT, 0644);
    }
    if(execvp(*no_of_arg, no_of_arg) < 0) {
      perror("execvp"); exit(1);
    }
  } else {
    //The parent:
    
    close(pipefd[1]);
    close(pipefd[0]);
    wait(&copy1);
    wait(&copy2);
    if (WEXITSTATUS(copy1) || WEXITSTATUS(copy2)) {
      fprintf(stderr, "performed" "\n");
    }
  }
}
void  parse(char *input_by_user, char **no_of_arg)
{
     while (*input_by_user != '\0') {        
          while (*input_by_user == ' ' || *input_by_user == '\t' || *input_by_user == '\n' )
               *input_by_user++ = '\0';    
          *no_of_arg++ = input_by_user;          
          while (*input_by_user != '\0' && *input_by_user != ' ' && 
                 *input_by_user != '\t' && *input_by_user != '\n') 
               input_by_user++;             
     }
     *no_of_arg = '\0';                 
}


int main() {
	do{
  //String to store the input CommandInput_by_users
  char str[1000],temp[1000];
  //String to store all commands for output
  char cmd[1000] = "None";
  //used in strtok_r for tokenising "str"
  char pipec[] = "|";
  //same a pipe but for tokenising the whole command into command and arguments
  char args[] = " ";
  //To store value if Background is present or not
  bool backG = false;
  //We will check if its first Input file or not
  bool firstI = true;
  //Similiar to firstI but for output files
  bool firstO = true;
  //To check if we are putting first command into cmd
  bool firstC = true;
  //Token number for looking if token in not an argument but only command
  int TokNo;
  //variable to store input files name;
  char inputfile[1000] = "None";
  //similiar to inputfile but for output files
  char outputfile[1000] = "None";
  
  int Error = 0;
  int pipecount = 0;
  int pipeNo = 0;
  
   printf ("IUPUI SHELL \n ");
  printf ("Enter the input: ");
  
  
  //geeting whole string from user.
scanf ("%[^\n]%*c", str);
strcpy(temp,str);

if(strcmp(str,"exit") ==0 ){
	printf ("Exiting shell ");
	exit(0);
}
  int i;
  for(i=0;i<strlen(str);i++){
    if(str[i] == '|'){
    	if(str[i-1]=='\0'){
    		Error = 3;
    	}else if(str[i+1] =='\0'){
    		Error = 4;
    	}
        pipecount++;
    }
  }
  
  int pipefd[2];
	  if (pipe(pipefd) < 0)
	    {
	      perror ("pipe error. exiting.....");
	      exit (0);
	    }
	    
  pipecount+=1;
  //context for strtok_r() as we are using nested  tokenising. We cant use strtok()
  char * pipeContext, * argsContext;
  
  //Converting str into tokens
  char * pipeToken = strtok_r(str, pipec, &pipeContext);
  if(Error == 0)
  while (pipeToken != NULL) {
    TokNo = 0;
    pipeNo++;
    
    
    char * argToken = strtok_r(pipeToken, args, &argsContext);
	
	if(Error == 0)
    while (argToken != NULL) {

      TokNo++;
      
      if (strcmp(argToken, "<") == 0 || (strcmp(argToken, "<<") == 0)) {
        argToken = strtok_r(NULL, args, & argsContext);
      
        if(pipeNo != 1){
        	Error = 6;
        	break;
        }
        if(argToken == NULL){
        	Error = 1;
        	break;
        }
        if (firstI) {
          firstI = false;
          //replacing "NONE" from input file. similiarly for every other symbol
          strcpy(inputfile, argToken);
           
        } else {
          strcat(inputfile, ", ");
          strcat(inputfile, argToken);
        }
      } else if (strcmp(argToken, ">") == 0 || (strcmp(argToken, ">>") == 0)) {
        argToken = strtok_r(NULL, args, & argsContext);
        
        
        if(pipeNo != pipecount){
        	Error = 7;
        	break;
        }
        if(argToken == NULL){
        	Error = 2;
        	break;
        }
        if (firstO) {
          firstO = false;
          strcpy(outputfile, argToken);
        } else {
          strcat(outputfile, ", ");
          strcat(outputfile, argToken);
        }
      } else if (strcmp(argToken, "&") == 0) {
		if(pipeNo == pipecount && temp[strlen(temp) - 1] == '&'){
			 backG = true;
        argToken = strtok_r(NULL, args, & argsContext);
		}

      } else {
          //Here we are just taking first token i.e., our command
        if (TokNo == 1) {
          if (firstC) {
            firstC = false;
            strcpy(cmd, argToken);
          } else {
            strcat(cmd, ", ");
            strcat(cmd, argToken);
          }
        }else{
         strcat(cmd, " ");
            strcat(cmd, argToken);
}
      }

      argToken = strtok_r(NULL, args, & argsContext);
    }

    pipeToken = strtok_r(NULL, "|", & pipeContext);

  }
  
  switch(Error){
  	case 0 : if(backG==true)
  	{
  	    printf("background process and process id = %d \n",getpid());
  	    break;
  	}
  char  *no_of_arg[64];  
  int k =0;
  while(temp[k]!='\0'){
  if( temp[k] == '\n') 
     temp[k] = '\0';
     k++;
     if(k==strlen(temp) -1)
     break;}
  parse(temp, no_of_arg);      
  deploy(no_of_arg,inputfile,outputfile);
  
  
  break;
    case 1 : printf("Error : < or << is not followed  by a filename. \n");break;
    case 2 : printf("Error : > or >> is not followed  by a filename. \n"); break;
    case 3 : printf("Error : pip with no proceeding command. \n");break;
    case 4 : printf("Error : pip with no succeding command. \n"); break;
    
    case 5 : printf("Error : input redirct after a pip; make sure only the first subcommand have < \n"); break;
    case 6 : printf("Error : input redirct after a pip; make sure only the last subcommand have > \n"); break;
    default : printf("SYSTEM FAILURE \n"); break;
  }
  
  
  
  
  
  }while(true);
  return 0;
}




HW2/readme.txt0000644003432100136040000000350513547515657013424 0ustar  singh96students1.C code is written in hw2.c file.
2.Makefile creates a executable file with the name of "hw2"
3.Tried implementing multiple pipes to an extend and this is the maximum that i
could get this shell working .

BUILD INFORMATION 

1. run make 
2. executable file hw1 will be made .
3. type ./hw2 and press enter (you will enter the shell ).
4. test for commands untill you press "quit".
5. shell will exit on typing exit.

"NEW FILES CAN BE SEEN AFTER WE EXIT THE SHELL BY TYPING exit "

TEST CASES(background process and all error cases ae working but multiple pipes work to an extend  )
SINGLE COMMANDS 
1.IUPUI SHELL
 Enter the input: grep printf | sort | more &
background process and process id = 200858

2.IUPUI SHELL
Enter the input: ls
hw2  hw2.c  Makefile  readme.txt

3.
IUPUI SHELL									 Enter the input: ls -lh
total 32K
-rwxr-xr-x 1 singh96 students  14K Oct  3 15:34 hw2
-rw-r--r-- 1 singh96 students 6.4K Oct  3 15:18 hw2.c
-rw-r--r-- 1 singh96 students   29 Oct  3 15:33 Makefile
-rw-r--r-- 1 singh96 students 1.4K Sep 16 09:42 readme.txt


4.
IUPUI SHELL
 Enter the input: ps
   PID TTY          TIME CMD
193640 pts/3    00:00:00 bash
194985 pts/3    00:00:00 hw2
195398 pts/3    00:00:00 ps
195399 pts/3    00:00:00 ps

5.
 IUPUI SHELL                                                                     
 Enter the input: grep fprintf hw2.c
  fprintf(stderr, "performed" "\n");
6.
MULTIPLE COMMANDS 

IUPUI SHELL                                                                      
Enter the input: grep fprintf hw2.c | sort hw2.c
hw2.c:      fprintf(stderr, "performed" "\n");
sort:      fprintf(stderr, "performed" "\n");
performed

ERROR CASES
7.IUPUI SHELL									  // output should be in the last and input at starting 
 Enter the input: output > a.txt | cat
Error : input redirct after a pip; make sure only the last subcommand have >