Thread: I/O Problems - fstream

look at outdata.txt to make sure it data got written correctly. You can comment out everything after closing inData and before reopening it to try to get it to run to this point first, because what you have looks like it should work. If it writes to outdata.txt ok then display just total and count after reading them in and not do the avg calculation. Those steps should help you localize the problem.

Don't have my compiler available at this time to run your code. If you haven't figured it out by time I have it available I will compile it and let you know.

For now I would try placing a series of cout statements after each critical step to see exactly where things are getting hung up when you try to run the entire program.

PHP:--------------------------------------------------------------------------------
#include <iostream>
#include <fstream>

using namespace std;

int main()
{
int count = 0;
int num = 0;
int total = 0;
int avg = 0;

ifstream inData;
ofstream outData;

inData.open("datfile1.txt");
outData.open("outdata.txt");

// check if the open calls actually succeeded !!!
if(!infile)
{
cout << "unable to open file on first attempt" << endl;
}

while(inData >> num)
{
outData << num << " ";
cout << num << " ";
}

outData << endl;
cout << endl;

inData.close();

// lets get the avg of all ints in the file

inData.open("datfile1.txt");

if(!infile)
{
cout << "unable to open file on second attempt" << endl;
}


while(inData >> num)
{
outData << num << " ";

total += num;
cout << num << endl;
count++;
cout << count << endl;
}

avg = total/count;

outData << endl << avg << endl;
cout << avg << endl;

inData.close();
outData.close();

return 0;
}

I also might try using a second ifstream to read in the second time or commenting out the first call to inData.close() and the second call to inData.open().

I might also try making sure inData closed when it should have by commenting out the second call to inData.open() and see if you get the appropriate cout statement. You probably should comment out the second while loop if you do this though.

Good luck. I'll try to check back later.

Kinda new at file io but doesn't the first instance of a stream being attached to a file make it read and write protected from other streams unless specified not to be?

I pasted and compiled the code with all the couts listed. It ran fine. Then I took all the couts out and just ran the basic program. It ran and gave correct calculation of file (well, I did change avg to type float, but that doesn't matter much.) I use B4.52 as my IDE. I looked up the member functions for ifstreams. open() is listed, but close() is not. I looked up close() in my reference text, and it is clearly used in programs there in conjunction with ifstreams. I commented out the second call to inData.open() and it crashed. I used tellg() to find out the file cursor position at the end of the first while loop and then again after opening the file for the second time. The file positions were appropriate (at least the file pointer position went from 33 after the first loop and before closing inData to 0 after opening the file for the second time).

Maybe you can try retyping the lines with close() and the second call to inData.open(). Otherwise I am flumuxed, too. The code looks correct.

If you know anybody with the same compiler you are using you can try your source code there. If your source code runs on a different compiler, then I suspect you have an error in the software of your compiler.

As I said, your code closing and reopening the ifstream seems to work fine on my compiler.


You could try resetting the file pointer using seekg() rather than closing and reopening the file, although I have to say I had trouble trying to do that when I was goofing around with the code. If you want to try it, look up what header seekg() is in and #include it. then comment out the call to close() and the second call to inData.open(). Place the line:

inData.seekg(0);

immediately after the commented out call to open(). And try compiling/running.

Are you sure the code you initially posted is symbol for symbol the same as the code you are trying to run?

Being self_taught I used to run into these sorts of snafu's all the time. Getting better now, though still a lot to learn.

Idn't life wunerful?