How to check whether a system is big endian or little endian?

Question

How to check whether a system is big endian or little endian?

Answer 1

In Rust (byteorder crate required):

use std::any::TypeId;

let is_little_endian = TypeId::of::<byteorder::NativeEndian>() == TypeId::of::<byteorder::LittleEndian>();

Answer 2

A C++ solution:

namespace sys {

const unsigned one = 1U;

inline bool little_endian()
{
    return reinterpret_cast<const char*>(&one) + sizeof(unsigned) - 1;
}

inline bool big_endian()
{
    return !little_endian();
}

} // sys

int main()
{
    if(sys::little_endian())
        std::cout << "little";
}

Answer 3

In Linux,

static union { char c[4]; unsigned long mylong; } endian_test = { { 'l', '?', '?', 'b' } };
#define ENDIANNESS ((char)endian_test.mylong)

if (ENDIANNESS == 'l') /* little endian */
if (ENDIANNESS == 'b') /* big endian */

Answer 4

In C++20 use std::endian:

#include <bit>
#include <iostream>

int main() {
    if constexpr (std::endian::native == std::endian::little)
        std::cout << "little-endian";
    else if constexpr (std::endian::native == std::endian::big)
        std::cout << "big-endian";
    else
        std::cout << "mixed-endian";
}

Answer 5

In Nim,

echo cpuEndian

---

It is exported from the system module.

Answer 6

If you are using .NET: Check the value of BitConverter.IsLittleEndian.