Thread: check if a file is already open

The easiest and cleanest way would be something like a wrapper function to open the file.

Code:

void wrapper ( char *filename ) {
  FILE *fp = fopen(filename,"r");
  recursive(fp);
  fclose(fp);
}

This is fugly

Code:

void recursive ( char *filename ) {
  static FILE *fp = NULL;
  if ( !fp ) {
    fp = fopen(filename,"r");
    // read from static fp
    recursive(filename);
    fclose(fp);
    fp = NULL;
  } else {
    // read from static fp
    recursive(filename);
  }
}

Finding out whether the file is open would involve expensive OS calls (and be very non-portable).