text: #include "apue.h"
  #include "dirent.h"
  
  int main(int argc, char* argv[]) {
  
      DIR* dp;
      struct dirent *dirp;
      if (argc != 2) {
          err_quit("usage: ls directory_name");
      }
      if ((dp = opendir(argv[1])) == NULL) {
          err_sys("cannot open %s", argv[1]);
      }
      while ((dirp = readdir(dp)) != NULL) {
          printf("%s\n", dirp->d_name);
      }
      closedir(dp);
  
      exit(0);
  }