example of super basic ls implementation in c to build `gcc ls.c`

ls.c

#include <stdio.h>
#include <dirent.h>

int main (int argc, char *argv[ ])
{
  DIR *dp;
  struct dirent *dirp;
  
  if (argc != 2) {
    fprintf(stderr, "usage: ls directory_name\n");
    return 1;
  }

  if ((dp = opendir(argv[1])) == NULL) {
    perror("can't copen");
    return 2;
  }
  
  while((dirp = readdir(dp)) != NULL)
    printf("%s\n", dirp->d_name);
  
  closedir(dp);
  return 0;
}