Dump binary representation of IEEE double.

to_bytes.cpp

#include <memory>
#include <cstddef>
#include <algorithm>

#include <iostream>
#include <iomanip>

template<class T>
inline std::unique_ptr<unsigned char[]> to_bytes(const T& item)
{
    std::unique_ptr<unsigned char[]> buf(new unsigned char[sizeof(T)]);
    const unsigned char *p = reinterpret_cast<const unsigned char*>(&item);
    std::copy(p, p + sizeof(T), &buf[0]);
    return buf;
}

int main(int argc, char* argv[])
{
    if (argc != 2) {
        std::cerr << "Usage: " << (argc ? argv[0] : "to_bytes") << " <num>\n";
        return 0;
    }

    double d = std::strtod(argv[1], nullptr);
    auto b = to_bytes(d);
    std::cout << std::hex << std::setfill('0');
    for (std::size_t i = 0; i < sizeof(double); ++i)
        std::cout << std::setw(2) << static_cast<unsigned int>(b[i]) << ' ';
    std::cout << '\n';
}