I'm trying to determine the size of an error log file created by the code
below . More precisely if it isn't empty.
Is there any simple way to do that?
It would be great also to be able to send it to a mail client if it wasn't
empty, a hint on this would be enough.

TIA
SC

////////////////////////code
 FILE *ptf;

 Error_file="D:\\Error_log.txt";
 ptf = fopen (Error_file, "w+");

switch(error_condition) {
case 1
    fputs("Error in......", ptf);
    break;
// several case statements folowing....

long save = ftell(ptf);
fseek(ptf, 0, SEEK_END);
long file_size = ftell(ptf);
fseek(ptf, save, SEEK_SET);

2. Using GetFileSize (Windows API, required for 64-bit files)

HANDLE hFile = CreateFile(
  Error_file,
  GENERIC_READ|GENERIC_WRITE,
  0,
  0,
  OPEN_EXISTING,
  0,
  0);
if (hFile != INVALID_HANDLE_VALUE)  
  DWORD file_size = GetFileSize(hFile, 0);