Namespaces
Variants
Actions

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

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

Returns true if the most recent I/O operation on the stream completed successfully. Specifically, returns result of rdstate() == 0.

See ios_base::iostate for the list of conditions that set the stream status bits.

Contents

[edit] Parameters

(none)

[edit] Return value

true if the stream error flags are all false, false otherwise.

[edit] Example

Run this code
#include <cstdlib>
#include <fstream>
#include <iostream>
 
int main()
{
    const char* fname = "/tmp/test.txt";
    std::ofstream ofile{fname};
    ofile << "10 " << "11 " << "12 " << "non-int";
    ofile.close();
 
    std::ifstream file{fname};
    if (!file.good())  
    {  
        std::cout << "#1. Opening file test.txt failed - "
                     "one of the error flags is true\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 << "#2. I/O error while reading - badbit is true\n";
        return EXIT_FAILURE;
    } 
    else if (file.eof())
        std::cout << "#3. End of file reached successfully - eofbit is true\n"
            "This is fine even though file.good() is false\n"; 
    else if (file.fail())
        std::cout << "#4. Non-integer data encountered - failbit is true\n";
}

Possible output: 

10 11 12 
#4. Non-integer data encountered - failbit is true

[