Generating Output File Names on the fly

[Computergeek01]

Hey everyone, I am stuck and I keep going around in circles.

PROBLEM: I have a program that is reading data from a text file and sorting it into other files, these output files can only be so many lines long befor I need to make another.
QUESTION: How do I generate file names of output files to as I need them?

Pseudo-Code Example:
Entries 1-20 go to File1.
if more exist
Make File2
Entries 21-41 go to File2.
if more exist...

I'm reading thing in fine and sorting them to the file as I need but I cannot figure out how to change the file name after it is full.

Thanks for your help guys.

[Computergeek01]

I've tried changing the value of a pointer that is passed to ofstream and holds the file name, this causes errors when I compile.

I'm thinking of launching the create_file and the sort_data in functions and having those grab the ofstream file name from variables that I change then pass to them when ever the files have reached a certain size.

[Zhuge]

Just musing, but I would have an integer counter that has the file "number" you are currently on (File1, it would be 1, etc.). Then you can use a stringstream to create the filename like so:

int file_counter;
// ...
std::stringstream ss;
ss<<"File"<<file_counter;
std::string Filename = ss.str();

[Computergeek01]

I tried something like this, the problem I ran into was that the ofstream didn't change even though the string I passed to it with the file name did. I tried running it as a function and passing the new filename thinking that it would make an output file based on what I feed it but I did a cout inside the function and it still had the origional ouput file name. This is becoming more of a thought excercise for me as I found a work around for the project. There has to be a way I doubt I'm the only one in history who wanted to do this in C\C++.

[Computergeek01]

For anyone who is wondering my workaround sucks but it gets the job done. I kill the stream to the output file then call a function to rename it based on the string I pass to it. When the function returns a success I open the output stream again for the next set of data, if the function fails I run a few checks and respond according to what I find.

[steve yates]

Are you sure you are closing the old file before trying to open the new file? If the old file isn't closed, you'll get the problem you're running into.

[Computergeek01]

For my work around? Yeah that works fine I just don't like it. I am wondering about the first thing and I put the workaround in as a foot note.