Subject: File I/O question
Date: Wed, 21 May 2003 19:14:34 -0400
MIME-Version: 1.0
Content-Type: text/plain;
	charset="iso-8859-1"
Message-ID: <795DD3C2E97585449DCDEEE79CCD5C22BB5D@email2k.compuweigh.com>
X-MS-Has-Attach: 
X-MIMEOLE: Produced By Microsoft Exchange V6.0.6249.0
X-MS-TNEF-Correlator: 
content-class: urn:content-classes:message
Thread-Topic: File I/O question
Thread-Index: AcMf7r0W2NMg7hS1T12/aR7+hw6hIQ==
From: "Alex O" <Alex AT compuweigh DOT com>
To: "DJGPP (E-mail)" <djgpp AT delorie DOT com>
Content-Transfer-Encoding: 8bit
X-MIME-Autoconverted: from quoted-printable to 8bit by delorie.com id h4LN8np04850

Hi everybody,

Can somebody explain me what is wrong with the following code snippet?
The reason I am asking is because the original file WATTCP.CFG never gets changed!
As you can see, I tried two different functions to write data to the file and each one of those returned the correct number of characters written,
but when I go to view the file it is not even touched (even the file date is not changed). How come?

BTW, does fgets() move the file pointer as it advances?

...
  if( (ptr = fopen("wattcp.cfg", "r+")) != NULL )
  {
    while( fgets(tmp_buf, 99, ptr) )
    {
      //Skip the comment lines
      if( tmp_buf[0] != '#' )
      {
        if( !strncmp(tmp_buf, "my_ip = ", 8) )
        {
          _inet_ntoa((CHAR *)ip_buf, nonvol->IP_Addr);
          n = fprintf(ptr, "my_ip = %s  ; mandatory\n", ip_buf);
        }
        else if( !strncmp(tmp_buf, "netmask = ", 10) != NULL )
        {
          _inet_ntoa((CHAR *)ip_buf, nonvol->Subnet_Mask);
          sprintf(tmp_buf, "netmask = %s  ; mandatory if not using DHCP\n", ip_buf);
          n = fwrite(tmp_buf, sizeof(BYTE), strlen(tmp_buf), ptr);
        }
      }
    }
    fclose(ptr);
  }
...

Thanks for any good advice how to make this thing work.

Regards,

Alex Oleynikov