Error numbers

Each of the macros defined in <cerrno> expands to integer constant expressions with type int, each with a positive value, matching most of the POSIX error codes. The following constants are defined (the implementation may define more, as long as they begin with 'E' followed by digits or uppercase letters).

All values are required to be unique except that the values of EOPNOTSUPP and ENOTSUP may be identical and the values of EAGAIN and EWOULDBLOCK may be identical.

Example

#include <iostream>
#include <cmath>
#include <cerrno>
#include <cstring>
#include <clocale>
 
int main()
{
    double not_a_number = std::log(-1.0);
    if (errno == EDOM) {
        std::cout << "log(-1) failed: " << std::strerror(errno) << '\n';
        std::setlocale(LC_MESSAGES, "de_DE.utf8");
        std::cout << "Or, in German, " << std::strerror(errno) << '\n';
    }
}

log(-1) failed: Numerical argument out of domain
Or, in German, Das numerische Argument ist ausserhalb des Definitionsbereiches

See also