Reading from a text file

This is a discussion on Reading from a text file within the C++ Programming forums, part of the General Programming Boards category; Ok, so I have the following code, heres the problem. The program involves if/ else if statements, and I need ...

  1. #1
    Registered User
    Join Date
    Mar 2006
    Posts
    36

    Reading from a text file

    Ok, so I have the following code, heres the problem. The program involves if/ else if statements, and I need the program to be able to display the help.txt when the user decides to take that route. For some reason, when I do 'h' it is displayed the first time, then if i try the very next time to do 'h' it takes me back to the menu and nothing is displayed. It looks right to me, what am I missing? (i just put the important parts of the program here)
    Code:
      string file= "help.txt";
      string line;
      ifstream help;
    	
    if (choice =='h')
    {//Open choice ==h
    	 
    help.open (file.c_str());
    while (getline(help, line))
    cout << line << endl;
    help.close ();
    	
    }//End choice ==h

  2. #2
    Registered User
    Join Date
    Feb 2006
    Posts
    312
    How do you retrieve choice (which I assume is type char) from your user? are you using
    Code:
    cin >> choice;
    without clearing the cin stream before retrieving another value?

  3. #3
    Registered User
    Join Date
    Mar 2006
    Posts
    36
    well, heres what i got basically:

    Code:
    int main () {
    string file= "help.txt";
      string line;
      ifstream help;
      ofstream PC;
    int minutes, calc;
    double fee;
    
      char choice;
    
      while (choice)
      {//Open while
    
      cout << "Help     etc etc etc.........  Quit" << endl;
    cin >> choice;
    cin.ignore();
    	
    if (choice =='h')
    {//Open choice ==h
    help.open (file.c_str());
    while (getline(help, line))
    cout << line << endl;
    help.close ();
    }//End choice ==h
    etc etc etc..........

  4. #4
    Registered User whiteflags's Avatar
    Join Date
    Apr 2006
    Location
    United States
    Posts
    7,763
    Code:
    char choice;
    
    while (choice)
    I have a problem with these two lines right away. A good programming practice is to initialize your variables, and this is a perfect example of why.

    Since choice is set to NULL, the while loop shouldn't even run once.

    Using a do/while loop might be a solution, but maybe you should just initialize choice to some character.
    Last edited by whiteflags; 04-20-2006 at 08:54 PM.

  5. #5
    Registered User
    Join Date
    Feb 2006
    Posts
    312
    I agree - a do/while loop is certainly more suited to this kind of thing than a while loop

  6. #6
    Registered User
    Join Date
    Mar 2006
    Posts
    36
    I did as yall said but still the same problem, the help.txt is only displayed once, but when I try one of my other options multiple times, it works. I think there is something wrong with the way I coded the program to read the txt, any ideas?

  7. #7
    Registered User whiteflags's Avatar
    Join Date
    Apr 2006
    Location
    United States
    Posts
    7,763
    You wrote the lines just fine.

    There is something else I forgot to mention, yes.

    It's like the variable help fell out of scope. To keep help in scope, do this:

    Code:
    if (choice =='h')
    {//Open choice ==h
       ifstream help;
       help.open (file.c_str(), ifstream::out); // enable the file for output just to be sure
       while (getline(help, line))
          cout << line << endl;
       help.close ();
    }//End choice ==h
    Last edited by whiteflags; 04-20-2006 at 10:16 PM.

  8. #8
    Registered User
    Join Date
    Jan 2005
    Posts
    7,344
    You are re-using the help ifstream. The first time through it reads until it errors out (because it reaches the end of the file). The second time through the fail flag is still set, so it doesn't read anything.

    The solution is to call clear() to clear the flags in the stream before reading from it.

    You don't have to reduce the scope of the ifstream if you call clear, but it would be better practice to use that solution which minimizes the scope of the variable to the block of code that uses it.

  9. #9
    Registered User
    Join Date
    Mar 2006
    Posts
    36
    Great!!! both methods worked thanks ev1 for your help.

    hopefully, time to wrap this prog up....

Popular pages Recent additions subscribe to a feed

Similar Threads

  1. Formatting the contents of a text file
    By dagorsul in forum C++ Programming
    Replies: 2
    Last Post: 04-29-2008, 01:36 PM
  2. Inventory records
    By jsbeckton in forum C Programming
    Replies: 23
    Last Post: 06-28-2007, 05:14 AM
  3. C++ std routines
    By siavoshkc in forum C++ Programming
    Replies: 33
    Last Post: 07-28-2006, 01:13 AM
  4. Reading Character at a time from a text file
    By Giania in forum C Programming
    Replies: 8
    Last Post: 02-25-2006, 03:17 PM
  5. A bunch of Linker Errors...
    By Junior89 in forum Windows Programming
    Replies: 4
    Last Post: 01-06-2006, 02:59 PM

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21