reading from a file to linked list

This is a discussion on reading from a file to linked list within the C++ Programming forums, part of the General Programming Boards category; I'm having a little trouble reading a file into a linked list (which I'm just learning). The code I have ...

  1. #1
    Registered User
    Join Date
    Apr 2002
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    5

    reading from a file to linked list

    I'm having a little trouble reading a file into a linked list (which I'm just learning). The code I have is:
    Code:
    	
    	struct stock
    	{
    		char isbnChar[10],
    			 bookNoChar[10], 
    			 borrowedFromDate[3], 
    			 loanLengthChar[3], 
    			 currentBorrowerNo[5], 
      			 lastBorrowerNo[5],
    			 status[2];
    		struct stock * next;
    		int j;
    
    	};
    
            stock *root = NULL;
    	stock *curr = NULL;
    
    	ifstream IssueBook("stock.txt", ios::in);
    	if (!IssueBook)
    		cerr << "File Ccould not be opened" << endl;
    	do
    	{
    		IssueBook.getline(curr->bookNoChar, 5, ',');
    		IssueBook.getline(curr->isbnChar, 10, ',');
    		IssueBook.getline(curr->borrowedFromDate, 3, ',');
    		IssueBook.getline(curr->loanLengthChar, 3, ',');
    		IssueBook.getline(curr->lastBorrowerNo, 3, ',');
    		IssueBook.getline(curr->currentBorrowerNo, 3, ',');
    		IssueBook.getline(curr->status, 2, '\n');
    		if (strcmp(curr->bookNoChar,bookNumChar))
    			strcpy(curr->status, "O");
    		curr->next = new stock;
    		curr = curr->next;
    	}
    	while( !IssueBook.eof()  );
    	IssueBook.close();
    It doesn't like IssueBook.getline(curr->bookNoChar, 5, ','); and crashes straight away.

    The code should read comma sepparated values from a file into the list and change one value (in the if statement). Then I'll traverse the list putting the values back into the file with the updated one ammended.

  2. #2
    Snior Member
    Join Date
    Jan 2002
    Posts
    982
    curr is just a pointer. If you want to try and access something that it points to, you'll have to point it somewhere (at a stock instance created on the heap or stack).

  3. #3
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    Apr 2002
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    5
    Oh yeah sorry missed that bit of code. I've now put in
    root = new stock;
    I think I'm on my way now just hard getting used to it all


  4. #4
    Registered User
    Join Date
    Apr 2002
    Posts
    5
    Now I'm stumped as to why instead of it reading the values:
    1,1,100,21,***,***,S
    it reads
    1,1,100, ,21,***, ,

    Is there something wrong with my getline statements because they work ok in the rest of the program.

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