Directions: Modify your code below so that it implements the following internal

Question

Directions:

Modify your code below so that it implements the following internal commands:
1. pwd Print current working directory.
2. cd [dir] Change directories.
3. exit Terminates the shell

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <readline/readline.h>
#include <readline/history.h>
#include <curses.h>
#include <string.h>

extern char **environ;
int main(int argc, char **argv)
{
   char *s;
   char *token;
   int count = 0;
   int command = -1;
   char *name;
  
   while ((s=readline("prompt>")) != NULL) // reads from the command line
   {
       token = strtok(s, " "); // calls the strtoks function
       while(token != NULL) //Running through the loop
       {
      
           if (count == 0)
           {
               if (strcmp (token, "set") == 0) //set command
               {  
                   command = 1;
               }
               else if (strcmp (token, "delete") == 0) //delete command
               {
                       command = 2;
               }
               else if (strcmp (token, "print") == 0) //print command
               {
                       command = 3;
               }
           }
           else if (count == 1) // Goes through the while loop
           {
                   if (command == 1) //set the value of of the enviornment variable with varname
                   {
                       name = token;
                   }
                   else if (command == 2) //removes the enviorment variable
                   {
                       unsetenv(token);
                   }
                   else if (command == 3)//prints the environment variable
                   {
                       printf("%s = %s ",token,getenv(token));
                   }

           }
           else if (count == 2)
           {
           }
           else if (count == 3) //sets the value of the variable name
           {
                   setenv(name, token, 1);
           }

           token = strtok(NULL, " ");
           count++;
       }
           count = 0;
           add_history(s); /* adds the line to the readline history buffer */
           free(s); /* clean up! */
      
   }
       return(0);
}

Explanation / Answer

  
   #include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <readline/readline.h>
#include <readline/history.h>
#include <curses.h>
#include <string.h>

extern char **environ;
int main(int argc, char **argv)
{
char *s;
char *token;
int count = 0;
int command = -1;
char *name;
  
   //Added these lines.
   chdir("/path/to/change/directory/to");
getcwd(cwd, sizeof(cwd));
  
while ((s=readline("prompt>")) != NULL) // reads from the command line
{
token = strtok(s, " "); // calls the strtoks function
while(token != NULL) //Running through the loop
{
  
if (count == 0)
{
if (strcmp (token, "set") == 0) //set command
{
command = 1;
}
else if (strcmp (token, "delete") == 0) //delete command
{
command = 2;
}
else if (strcmp (token, "print") == 0) //print command
{
command = 3;
}
}
else if (count == 1) // Goes through the while loop
{
if (command == 1) //set the value of of the enviornment variable with varname
{
name = token;
}
else if (command == 2) //removes the enviorment variable
{
unsetenv(token);
}
else if (command == 3)//prints the environment variable
{
printf("%s = %s ",token,getenv(token));
}
}
else if (count == 2)
{
}
else if (count == 3) //sets the value of the variable name
{
setenv(name, token, 1);
}
token = strtok(NULL, " ");
count++;
}
count = 0;
add_history(s); /* adds the line to the readline history buffer */
free(s); /* clean up! */
  
}
return(0);
}

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