Writing to a file problem

[therry1]

Hi all,
I have a problem writing to a file. I don't know where I'm wrong.
Any help will be greatly appreciated. My code is:

#include <iostream>
#include <math.h>
#include <fstream>
#include <ios>
using namespace std;

int main()
{
	long double x = 0;
	long double y = 0.0000001;
	long double z = 0;

	ofstream a_file ( "C:\\tmci\\RawData\\Sqr_root.txt",  ios::app );
	if (! a_file )
	{
		cout << "Can't open input file " << " Sqr_root.txt " << endl;
		cin.get();
		exit(1);
	}

	for (int i = 0; i < 49; i++ )
	{
		x = (x + y);
		cout << x ;
		z = (x * x);
		cout << "    " << z << endl << endl;

		a_file <<  x << "    " << z ;

		//system ("Pause");
	}

	system ("Pause");
	return 0;
}

[BlackSheep]

1. Why do you create a_file? It serves no purpose. b_file will create the requested file since it is an outstream.

2. You don't need to keep re-opening b_file during your for loop. Initialize it right before the loop itself.

3. Your problem is probably due to admin rights.

[Staceyery]

I have same problem...

[therry1]

Blacksheep, thanks for your reply. As seen above, I followed your suggestion but my program still does not write to a_file. What am I doing wrong? Can you please give me an example? Thanks. . . . therry

[whitenite1]

@therry1

I compiled your program, and it worked perfectly, after I created the 'tcmi' and 'RawData' directories in the root of the C drive, since that is where the program is looking for it.

[therry1]

whitenite1, thanks for your reply. What would stop it from working on my computer? I use Windows 7 (x64) and Microsoft visual studio pro 2010. It works perfectly on screen, but it will not write to the file.
Thanks. . . .therry

[whitenite1]

@therry1

Not sure, since I also use Windows 7 on a x64, and I use Visual Studio 2012 Express. The only thing that comes to mind is that one of the two directories, have a different spelling than what you're looking for in the program. Try removing "C:\\tmci\\RawData\\Sqr_root.txt" and replace it with just "Sqr_root.txt" instead. Then check the directory the <name of your program>.cpp is in, and see if the text file is in there. If it is, then the location you were checking originally, must be wrong. Hope this helps..

[dovip]

Hmm. Seemly worked it..fine because I am using on Dev C++ and Windows Vista.

[therry1]

whitenite1, Thanks for your help. I've tried everything that I could think of. Since the search for the file is outside of the for loop, it has no effect on the program. I'm beginning to suspect the line a_file << x << " " << z ; I don't know if it is really correct. . . or is there another way to write to a file? I wonder why the program does not complain when I build it. . . .therry

[whitenite1]

@therry1

I modified your program a bit, by removing the #include <ios> ,
and the if(! a_file) section. This still works. Try it.

// Write File.cpp : main project file.
#include <iostream>
#include <math.h>
#include <fstream>

using namespace std;

int main()
{
	long double x = 0.0;
	long double y = 0.01;
	long double z = 0.0;
	ofstream a_file( "C:\\tmci\\RawData\\Sqr_root.txt"); // Or try changing to
                                            // ofstream a_file( "C:\\Temp\\Sqr_root.txt");, then check Temp dir for result
		
	for (int i = 0; i < 49; i++ )
	{
		x = (x + y);
		cout << x ;
		z = (x * x);
		cout << "   " << z << endl;

		a_file <<  x << " " << z << endl; // Added a newline, so each set of numbers is on a separate line

	}
	a_file.close(); // Probably not needed, but still good idea to close files 
	system ("Pause");
	return 0;
}

[therry1]

whitenite1, thanks again for your replies. I tried the above code, it reacts the same as mine. Both works well on screen, but both will not write to a_file regardless of the directory that Sqr_root.txt is in. If the above code writes to a_file on your computer, can you please email me a copy of "Sqr_root.txt" file so I can check it against my computer? Send it to <[e-mail]>. I now question my computer installation of my compiler. . . thanks again,. . . . therry