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std::basic_ios<CharT,Traits>::operator!

From cppreference.com
< cpp‎ | io‎ | basic ios
 
C++
 
Input/output library
 
std::basic_ios
 
bool operator!() const;

Returns true if an error has occurred on the associated stream. Specifically, returns true if badbit or failbit is set in rdstate().

Contents

[edit] Parameters

(none)

[edit] Return value

true if an error has occurred, false otherwise.

[edit] Example

Run this code
#include <cstdlib>
#include <fstream>
#include <iostream>
 
int main()
{
    std::ifstream file("test.txt");
    if (!file) // operator! is used here
    {  
        std::cout << "File opening failed\n";
        return EXIT_FAILURE;
    }
 
    // typical C++ I/O loop uses the return value of the I/O function
    // as the loop controlling condition, operator bool() is used here
    for (int n; file >> n;)
       std::cout << n << ' ';
    std::cout << '\n';
 
    if (file.bad())
        std::cout << "I/O error while reading\n";
    else if (file.eof())
        std::cout << "End of file reached successfully\n";
    else if (file.fail())