problem with ifstream--please help

SnaKeBeD

hai all, while i'm trying to read a text file using ifstream, my code is reading data when i run the code from my vc++ (VS 6.0) workspace in debug mode.My .txt file is in the workspace folder and i'm reading from there. My problem is even if the .txt file is not there,the code is not throwing any exception and doing some calculation. i like to know y is it so,also i have closed and cleared the file pointer still the problem exists ifstream ifs; ifs("sample.txt",ifstream::in); thanks in advance

swaroop

jhwurmbach

ifstream ifs;
ifs.open( "sample.txt", ifstream::in);
if( !ifs.is_open()) {
//Cry out
}

Though I speak with the tongues of men and of angels, and have not money, I am become as a sounding brass, or a tinkling cymbal.
George Orwell, "Keep the Aspidistra Flying", Opening words

SnaKeBeD

hi still the same problem exists.The code is not checking whether the file is opened or not, its getting some values from some other location.

swaroop

jhwurmbach

swaroopkb wrote:

still the same problem exists

And what is the problem? You are vague.

Though I speak with the tongues of men and of angels, and have not money, I am become as a sounding brass, or a tinkling cymbal.
George Orwell, "Keep the Aspidistra Flying", Opening words

SnaKeBeD

sorry for the troubles, could u please tell me how to close or destroy an ifstream object, i think thats the problem when the program run ifstream object is having the buff value, its not getting cleared. Even if the sample.txt file is not there the buff is showing the contents of sample.txt, could u please tell me y is it so ???:sigh:

swaroop

jhwurmbach

std::ifstream has a close()-function, which flushes all buffers and closes the file. It destructor is also calling close, so you could simply let the stream-object go out of scope. Hint: You can introduce a scope by simply opening a { writing your code and closing the scope with }

Though I speak with the tongues of men and of angels, and have not money, I am become as a sounding brass, or a tinkling cymbal.
George Orwell, "Keep the Aspidistra Flying", Opening words

Maxwell Chen

swaroopkb wrote:

the buff value, its not getting cleared

To clear the buffer of istream, use std::basic_istream::ignore.

std::fstream f("a.txt", std::ios::in);
std::cout << f.rdbuf();	// Display content: "ABCDEFG"
std::cout << "\\n---\\n";
std::streamsize n;
f.seekg(0, std::ios::end);
n = f.tellg();	// Get the file size.
f.seekg(0, std::ios::beg);
f.ignore(n);	// Flush buffer.
std::cout << f.rdbuf();	// Displays nothing.

Maxwell Chen

David Crow

Does this work?

void main( void )
{
std::ifstream ifs;

ifs.open("\\\\sample.txt");
if (! ifs.is\_open())
    std::cout << "File not opened\\n";
else
    std::cout << "File opened\\n";

}

"A good athlete is the result of a good and worthy opponent." - David Crow

"To have a respect for ourselves guides our morals; to have deference for others governs our manners." - Laurence Sterne