#include <stdio.h>
#include <stdlib.h>

void do_something_with_a_file(FILE *file) {
  // But what to do?
}

int main(int argc, char *argv[argc+1]) {
  if (argc < 2) {
    printf("Usage: %s <file to open>\n", argv[0]);
    return EXIT_FAILURE;
  }
  char *file_to_open = argv[1];
  FILE *file = fopen(file_to_open, "r");

  // fopen will return NULL (look at man page)
  if (file) {
    printf("File is #%d\n", fileno(file));

    do_something_with_a_file(file);
    
    fclose(file);
  } else {
    perror("Oh noes! Failed to open file");
    return EXIT_FAILURE;
  }


  return EXIT_SUCCESS;
}