Got the idea from https://stackoverflow.com/questions/12774207/fastest-way-to-check-if-a-file-exist-using-standard-c-c11-c

File Existence Checker

#include <sys/stat.h>
#include <stdio.h>

int main(int argc, char *argv[])
{
  if (argc != 2)
  {
    return 0;
  }

  struct stat buffer;
  
  if (stat(argv[1], &buffer) == 0)
  {
    printf("Yes.\n");
  }

  else
  {
    printf("No.\n");
  }

  return 0;
}

Now if only it were built-in, it could actually beat ls ...