#include <sys/wait.h>

#include <string.h>

#include <stdlib.h>

#include <stdio.h>

#include <unistd.h>

#include <dirent.h>



int parse(char* st, char** toks)

{

  char* tok = strtok(st," \t");

  int t = 0;

  while((tok != NULL) && (t < 10))

  {

    toks[t] = tok;

    t++;

    tok = strtok(NULL," \t");

  }

  toks[t] = NULL;

  return t;

}



void f_echo(char* st)

{

  write(1,st,strlen(st));

  //write(1,"\n",1);

}



void f_cd(char* st)

{

  chdir(st);

}



void f_pwd()

{

  char dir[50];

  getcwd(dir, 50);
  write(1,"Current directory")

  write(1,dir,strlen(dir));

  write(1,"\n",1);

}



void f_ls(char* st)

{

  DIR* dir;

  struct dirent* de;



  dir = opendir(st);

  while((de = readdir(dir)) != NULL)

  {

    write(1, de->d_name, strlen(de->d_name));

    write(1,"\n",1);

  }



  close(dir);

}



int main()

{

  char cmd[256];

  char* toks[10];

  int t = 0;

  do{

    write(1,">",1);

    int n = read(0,&cmd,256);

    cmd[n-1] = '\0';

    int tt = parse(cmd, toks);

    if (strcmp(toks[0],"cd") == 0)

    {

      f_cd(toks[1]);

      t=1;

    }



    if (strcmp(toks[0],"echo") == 0)

    {

      int c = 1;

      while (c < tt)

      {

        f_echo(toks[c]);

        write(1," ",1);

        c++;

      }

      write(1,"\n",1);

      t=1;

    }



    if (strcmp(toks[0],"pwd") == 0)

    {

      f_pwd();

      t=1;

    }



    if (strcmp(toks[0],"myls") == 0)

    {

      if (tt==1)

      {

         f_ls("./");

      }

      else

      {

        f_ls(toks[1]);

        t=1;

      }

    }

    if (t == 0)

    {

      int p=fork();

      if (p==0)

      {

        execvp(toks[0],toks);

        perror("Unknown command");

        exit(1);

      }

      else if (p>0)

      {

        wait(&p);

      }

    }

  } while (strcmp(toks[0],"exit") != 0);

  return 0;

}