ls: No such file or directory error

I am writing a very basic shell for my school. Even thought commands like "pwd" or "date" works when i try "ls" it shows me that "ls: No such file or directory error"

The code of my shell is bellow:

#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <stdlib.h>
int main()
{
int i;
char *line=(char *) malloc(1024*sizeof(char));

 while (1) {
   /* Print the command prompt */
   printf("$ ");
   fflush(stdout); /* Anagazei na trexei thn printf
   /* Read a command line */
   fgets(line, 1024, stdin);
  for(i=0;i<1024;i++){
   if(line[i]=='\n')
         {
           line[i]='\0';
         }
  }
  //printf("%s", line);
   pid_t pid = fork(); /* Dhmiourgei paidi. antigrafo diergasias. */
     if (pid==0){

           execlp(line,line);
      }
     else waitpid(pid,0,0);

  }
}