How do I get a file to truncate, not append upon closing the program. When I close it, it writes to the file, but instead of updating the numeric total count it appends to it. Using the IOS::ATE | IOS::OUT.
Any help appreciated as I'm new to this...
Turbo C++ v4.5 (Borland)
Try fstream.
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ios::ate puts the filepointer at the eof for input. the difference between ate and app is that ate lets you write over old data.
just use ios:ut and it will do what you want also there is ios::trunc which i think sets the file at 0 length, though i have never used it i personally use ios:
edit:
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-
C++ streams that write to file (fstreams in ios:
ofstream fout("myFile.txt");
opens the the file called myFile.txt in ios:
Many thanks for the replies. Will give it a shot. ps I used fstream <filenames> as a global, is this acceptable..?
Yes.....but, use of global variables unless no work around available is discouraged in every teaching item and by most programmers I respect.
Yes E-lad, I know. It's the way the college have shown us. Everything I read about is classes. When I wrote a program with classes the tutor wouldn't help me. ps I finally used IOS::TRUNC |IOS::OUT and it works. Now I just have to get the other file to read/write and I'm sorted. The code is for a PC diagnostic interface and I have to log total errors to date by category, eg, Post errors, keyboard errors etc. Used Indexes but it won't write to file so when I restart program it reads a blank file. Coding is as follows:
filecat.open("a:\\error_count.txt", ios::trunc | ios:
if (!filecat)
{
cout <<"Error initialising file > error_count.txt "<<endl;
}
else
{
for (int index =0; index<7; index++)
{
filecat <<errors[index].no_of_faults;
}
}
filecat.close();
there are 6 fault categories but it won't write to a file on exit.
As I've said, I'm only beginner at C++ and any books or web sites use classes...any help, thanks in advance...
You migth be restricted to using the ios::whatever syntax only when you declare the stream. If that is true then it could be:
ifstream filecat("a:\\error_count.txt", ios::trunc | ios:ut);
or
ifstream filecat (ios::trunc | ios
filecat.open("a:\\error_count.txt");
but not
filecat.open("a:\\error_count.txt", ios::trunc | ios:ut);
HTH.
Much appreciated Elad...will give it a shot...
