Thread: Change character in file?

Hi, been searching but can't find anything... no idea what search parameters to use, so excuse me if this has already been discussed somewhere!

I've got the following problem: I have a file that contains the following (example) data:

Manufacturer;Model;2007;Signal_Name;640;2;0;Tester ;0
Another_Manufacturer;Some_Model;2007;Signal2_Name; 756;4;0;Some_Tester;0
etc.

As you can see it's a ;-seperated file that contains signal information. Every new line in the file represents a new signal.
The final '0' on the line indicates the signal isn't processed yet (i.e. added to our signal database).

Now, what I need to do is, when the signal has been processed, replace that '0' with a '1'. I think this should be doable with pointers, but apparently I have too little knowledge about pointers to make this work.

Here's an example of what I thought is a solution - please note I know this example is 90% bollocks, it's a "road plan" rather than a code example:

Code:

   
   FILE *fpin;
   int signals_cnt=0;

    if((fpin = fopen(signal_file,"r+"))!=NULL)
    {
       while(fpin!=EOF)
       {
          fpin++;
          puts(fpin);
          if(fpin=='\n')
          {
             signals_cnt++;
             if(signals_cnt==processed_signal_number)
             {
                 fpin--;
                 fpin='1';
             }

          }

       } //  while(fpin!=EOF)

    }

So the idea is to check for a new line character to count the signal number, and when the desired signal number was found, change the 0 into 1.
Apparantly fpin (declared as a FILE type) doesn't like being played with (the fpin++ results in blabla on-screen).

Hope it's clear :S Any help would be greatly appreciated!

Thanks in advance, René