fprintf failing miserably, please help

[reillan]

Hello,

I have a program that, shortening it to get rid of some file reads, looks as follows:

  int ch;
  FILE *fp;
  fp=fopen("c:\\test.txt", "r+");
  FILE *finuse;
  finuse=fopen("c:\\finuse.txt", "w+");
  if(finuse == NULL) printf("%s", strerror(errno));
  system("PAUSE");
  if(fp == NULL) printf("%s", strerror(errno));
  else
  {
    int InStats=0;          //value to indicate position inside stats loop
    int i=0;                //Counter
    while((ch=fgetc(fp)) != EOF)
    {
       /*lots of testing of ch to position me within the file
 and get some other data I'm not worried about at the moment*/

              else if(ch=='\n' && InStats>9)
            {
              fprintf(finuse,"inuse: %s",inuse);
              fflush(finuse);
            }
    }
  fclose(fp);
  fclose(finuse);
  return 0;

I tried moving the finuse open and close to position them immediately around the fprintf statement, and that works great (except for the fact that I only get one line. This thing should print out 95 lines, but can only do so if I can keep finuse open across the entire iteration of fp reads).

So, am I missing something? Or, is there a way I can buffer all of this into something else (if I use a string, it has to be capable of holding 297,600 characters).

Thank you. Understand I'm a complete noob, so please be gentle.

[Elkvis]

the first thing I see is that you're checking fp for NULL long after you attempt to open the file, and in fact, after you try to open another file, making the value of errno completely useless when checking fp. if you're getting to the loop, then both files must be open, but beyond that, it's hard to say what exactly is going on here. another thing I see is that you're never incrementing InStats. with the given code, InStats can never be greater than 9, and I don't see where you're declaring inuse.

[reillan]

the first thing I see is that you're checking fp for NULL long after you attempt to open the file, and in fact, after you try to open another file, making the value of errno completely useless when checking fp. if you're getting to the loop, then both files must be open, but beyond that, it's hard to say what exactly is going on here. another thing I see is that you're never incrementing InStats. with the given code, InStats can never be greater than 9, and I don't see where you're declaring inuse.

Ah, good catch on the NULL, although I moved those statements around a bit to see if I could help alievate the problem and didn't. I tried to change it as follows and the program won't print anything to the screen other than the system pause:

  FILE *finuse;
  finuse=fopen("c:\\finuse.txt", "w+");
  if(finuse == NULL) printf("%s", strerror(errno));
  system("PAUSE");
  FILE *fp;
  fp=fopen("c:\\test.txt", "r+");
  if(fp == NULL) printf("%s", strerror(errno));
  else
  {

Not sure what on earth is causing that, but just putting it back to the way I posted above lets it print to the screen just fine (albeit still without editing the file).

As for InStats - yes, that's part of the code I omitted. I can confirm that it's working and incrementing, though, as if I do a printf instead of an fprintf (omitting finuse in the statement), it prints to the screen perfectly.

[tabstop]

I tried moving the finuse open and close to position them immediately around the fprintf statement, and that works great (except for the fact that I only get one line. This thing should print out 95 lines, but can only do so if I can keep finuse open across the entire iteration of fp reads).

Since the first thing fopen does is delete the file if it already exists, then that seems perfectly normal. If you don't want to delete the file every time you (re)open it, you need to use the "a" mode.

[reillan]

Woot, that fixed it. Thank you much!