fail() Function in file streams

[vinaynaikwad]

I have this below piece of code where I am reading a file line by line and printing the contents. The contents are printed properly but everytime I run the program, the failbit is set. Any problem with the program?? Please help.

char finalLine[255];
memset (finalLine, '\0', sizeof(finalLine));
inputFile.open ("test.txt");

if (inputFile.open())
{
    while((!inpurFile.eof()) || (!inputFile.fail()))
    {
         inputFile.getline(finalLine,255);
         cout << finalLine << endl;
    }
    if (inputFile.fail())
    {
	cout << "Error while reading file test.txt" << ". errno = " << strerror(errno) << endl;
    }
}

Output:
Contents are printed fine. But the following statement is also printed.
Error while reading file test.txt. errno = Error 0

Why is this line getting printed?

[coder777]

Why is this line getting printed?

Because you read beyond the end of file (the errno isn't set in this case)

[vinaynaikwad]

@coder777

Any better way to implement this? I want to prevent reading beyond EOF.

Thanks in advance.

[coder777]

there's no problem reading beyond eof. just don't cout the result.

you may write it like so:

    while(inputFile.getline(finalLine,255))
    {
         cout << finalLine << endl;
    }
    if (inputFile.fail() && (!inputFile.eof()))
    {
	cout << "Error while reading file test.txt" << ". errno = " << strerror(errno) << endl;
    }

btw: the better getline is this:

http://www.cplusplus.com/reference/string/getline/

with strings

[Cubbi]

Why is this line getting printed?

There can be two reasons:
1. istream::getline() encountered a line in your file that was more than 254 characters in length. It sets the failbit if it fails to get the entire line.
2 istream::getline() was unable to extract *any* characters, the file was empty or already at the end (your case), there was nothing more to read. It sets both eofbit and failbit in that case.

std::getline (the one that writes into strings) does the same thing when called with an empty file or file at end.

Based on you looking at errno, I think you meant to check for the badbit, not the failbit. The conditions that set failbit have no effect on errno in any case.

#include <iostream>
#include <fstream>
#include <string>
#include <cstring>
using namespace std;
int main()
{
    string finalLine;
    ifstream inputFile("test.txt");

    while(getline(inputFile, finalLine))
    {
         cout << finalLine << '\n';
    }

    if (inputFile.bad())
    {
        cout << "Error while reading file test.txt: " << std::strerror(errno) << '\n';
    }
}

PS: that memset() looks silly: first, you can initialize arrays to zero, second, you don't need to initialize them anyway if you're using istream::getline().