Thread: Help with output to files

I am trying to make a simple phone book. I've got everything all right right down to the actual output to the file.

Code:

    cout << "Is this information correct? (Y or N)";
                 ch = getch();
                 
                 if(ch == 'y' || ch == 'Y'){
                      ofstream file;
                      file.open("Book.txt", ios::ate);
                      file << data.fname << " " <<data.lname << endl
                           << data.phnum << endl
                           << data.addy << endl
                           << data.cmt << endl << endl;
                      file.close();
                      menu();
             }

I used ios::ate to open the file and go to the end of the file, but when I try to add a second entry, it overwrites the first.

Any help at all would be appreciated.

Thanks

You want "ios::ate | ios::out".

gg

My bad.
According to the C++ standard, ios::out is the equivalent of fopen()'s "w", that is a new file is created or an old one is truncated.
So in other words, "ios::out" and "ios::out | ios::trunc" will result in identical behavour.

Here's the table right out of the C++ standard:

Code:

B - ios::binary
I - ios::in
O - ios::out
T - ios::trunc
A - ios::app
Eq - fopen() equivalent

B I O T A Eq
--------------
    +     "w" 
    +   + "a" 
    + +   "w" 
  +       "r" 
  + +     "r+" 
  + + +   "w+" 
+   +     "wb" 
+   +   + "ab" 
+   + +   "wb" 
+ +       "rb" 
+ + +     "r+b" 
+ + + +   "w+b"

These are all the valid combinations and any combination not in the table should cause open to fail (this is rarely the case with most implementations).

Notice that ios::ate isn't even in the table. It's really just a flag to seek to the end of the file once the file has been opened.

If you really want to use ios::ate instead of ios::app, you have to open the file for output in a way that does not truncate the file - that is "ios::in | ios::out | ios::ate".

The difference between that and "ios::out | ios::app" is that ios::app causes all output to be appended to the file, regarless of an any seekp() calls.

gg

Thats no problem though.

Now I just need to figure out on my own a "search" feature which I am thinking would work with using getline() and setting every line to a variable, and then use str functions to read whats inside the strings.

Thanks again though.