std::optional<T>:: value_or

Returns the contained value if * this has a value, otherwise returns default_value .

Parameters

Return value

The current value if * this has a value, or default_value otherwise.

Exceptions

Any exception thrown by the selected constructor of the return value T .

Example

#include <cstdlib>
#include <iostream>
#include <optional>
 
std::optional<const char*> maybe_getenv(const char* n)
{
    if (const char* x = std::getenv(n))
        return x;
    else
        return {};
}
 
int main()
{
    std::cout << maybe_getenv("SHELL").value_or("(none)") << '\n';
    std::cout << maybe_getenv("MYPWD").value_or("(none)") << '\n';
}

/usr/bin/zsh
(none)

See also