std::basic_ios<CharT,Traits>::fail

#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())
 std::cout << "Non-integer data encountered\n";
}