Thread: Using fgets on a file

I am trying to write a program that will spell check a file by reading in two files. he problem I am having is that I have to enter the file containing a list of dictionary words into a binary search tree. I am trying to use fget to get all the words in the file into the tree. When I try it the way it is posted below only the first word goes through the insert function. When I try to write while(!feof(ifp)) it goes through all the words, but each word enters the BST on its own thus creating its own BST. I don't know how to get the words from the dictionary file into the BST and have it create a whole BST.

> (*root)->word = dictionary_words;
Try using strcpy() to make a copy of the word, and see if that helps:
strcpy((*root)->word, dictionary_words);

For some reason that cased my function to crash. I don't know why because it makes more sense then just setting them equal to each other. I read the FAQ about feof and loops and see that I shouldn't use while(!feof(ifp)) and replaced it with what is recommended in the FAQ.

I have no warnings or errors now. Now I think I should erase some of these printf functions. That last run took over 3 minutes to finish. It's still replacing the first word with the newest word entered. I removed \n from the words using strtok but I think it is still replacing the head node.

I ran your latest code with a test file and it seemed like the nodes were inserted into the tree. I created a function to print the tree afterwards, and it looked like the words were properly inserted. I didn't run the spellcheck part of your code.

http://cpwiki.sf.net/A_pointer_on_pointers
Unfortunately, an array cannot be copied by assign. Instead, by design, the address to the first element is returned so you'll be dealing with pointers instead. And when dealing with pointers, it's good to read up about them from that article.
This is why you can't simply a string - because you're going to make a copy of the pointer, which means the data itself won't be duplicated, only the address where the data is stored.

It also sounds like your code has a lot of problems or complexity in it. It might just be a ticking time bomb. Perhaps you should try posting your code, if not already done so elsewhere so someone can have a look.

Firstly, you need to do something about those scanf reading strings.
See http://cpwiki.sf.net/Buffer_overrun
And the problem, I think, may be your last loop:

Code:

	while(!feof(fin))
	{
		fgets(spellcheckwords, 1024, fin);
		   
		if(feof(fin))
		{
			break;
		}
		
		fixedlist = strtok(spellcheckwords, delimiters);
		
		while(fixedlist != NULL)
		{
			printf("\n%s\n", fixedlist);
			fixedlist = strtok(NULL, delimiters);
		}
	  }

Consider that fgets might read the last line in your file and encounters the end of file. The EOF flag gets set and the line isn't processed. You did it right before. Put the fgets as the loop condition. Fgets will return 0 if it didn't read anything.

Code:

		if(feof(ifp))
		{
			break;
		}

This is not needed if you check that fgets() returns not-NULL. If you have specific circumstances[1], the feof() will be true even if you managed to read something from the file, and that's obviously not particularly useful.

[1] Particularly if the file ends without a newline.

--
Mats

Originally Posted by Elysia

Firstly, you need to do something about those scanf reading strings.
See http://cpwiki.sf.net/Buffer_overruns
And the problem, I think, may be your last loop:

Consider that fgets might read the last line in your file and encounters the end of file. The EOF flag gets set and the line isn't processed. You did it right before. Put the fgets as the loop condition. Fgets will return 0 if it didn't read anything.

Thanks. I'll fix that right now. Thanks a lot for readings its helping me understand these concepts better. I updated my code and the scanf, but using fgets its not working. Do I have to do it a different way since I am reading a file? I tried sizeof(), but that didn't fix the problem either.

Originally Posted by MasterAchilles

Thanks a lot for readings its helping me understand these concepts better.

No problem about those. That's what they're for.
Oops, typo in link >_< Fixed now.