Can't open an fstream file

[giljo11778]

I'm using DEV-C++ 4.9.9.2

I'm having trouble opening files. Below is a simple listing that I can replicate the problem with on my workstation. The program compiles fine but when I run it, the file does not open and I get the exception list from the line if(!myfile). In all my searching on the web I'm seeing that this is the correct way to open a file for read/write in binary mode with append but it fails every time. However, if I compile this code on MSVC++ version 6, it runs correctly. Any ideas would be great.

Thanks,
giljo11778

include <iostream> // standard IO

include <conio.h> // getch

include <fstream> // File system IO access

using namespace std;

int main()
{
fstream myfile;
myfile.open ("count.dat", ios::in | ios::out | ios::binary | ios::app);
if (!myfile)
{
cout << "problem opening file\n";
cout << "end of file\t\t" << myfile.eof() << endl;
cout << "failed to open\t\t" << myfile.fail() << endl;
cout << "bad bit found\t\t" << myfile.bad() << endl;
cout << "everything is fine\t" << myfile.good() << endl;
cout << "any key to cont.\n";
getch();
exit(1);
}
return 0;
}

output from the program:

problem opening file
end of file 0
failed to open 1
bad bit found 0
everything is fine 0
any key to cont.

Compile log:Compiler: Default compiler
Building Makefile: "C:\Cprojects\BOOP\chapter_12\exercise_1\Makefile.win"
Executing make...
make.exe -f "C:\Cprojects\BOOP\chapter_12\exercise_1\Makefile.win" all
g++.exe -c main.cpp -o main.o -I"C:/Dev-Cpp/lib/gcc/mingw32/3.4.2/include" -I"C:/Dev-Cpp/include/c++/3.4.2/backward" -I"C:/Dev-Cpp/include/c++/3.4.2/mingw32" -I"C:/Dev-Cpp/include/c++/3.4.2" -I"C:/Dev-Cpp/include"

g++.exe main.o -o "filing_distnaces.exe" -L"C:/Dev-Cpp/lib"

Execution terminated
Compilation successful

[Nobody/Anonymous]

It seems, you can't open a file in append mode and read mode combined.
With ios::out | ios::binary | ios::app, it works fine.

If you need it in read/write mode, you can control the output pointer position with seekp:
http://www.cplusplus.com/reference/iostream/ostream/seekp.html

leo_sc

[giljo11778]

Ok, problem resolved. I looked at the seekp page and could set it, however, since the file was not set to ios::in I could not read from the file. A little more searching and I found that a file opened with ios::ate also opens with the output pointer at the end of the file but I can use both ios::in and ios::out on that file so I can set the input pointer with seekg() to the top of the file and read back the whole thing.

Thanks for pushing me in the right direction.

giljo11778