C program to check little vs big endian

Question

Possible Duplicate    C Macro definition to determine big endian or little endian machine        int main       int x   1     char  y    char   amp x     printf   c n   y 48       If it s little endian it will print 1   If it s big endian it will print 0   Is that correct   Or will setting a char  to int x always point to the least significant bit  regardless of endianness

User · Answer

Thought I knew I had read about that in the standard; but can't find it. Keeps looking. Old; answering heading; not Q-tex ;P:

The following program would determine that:

#include <stdio.h>
#include <stdint.h>

int is_big_endian(void)
{
    union {
        uint32_t i;
        char c[4];
    } e = { 0x01000000 };

    return e.c[0];
}

int main(void)
{
    printf("System is %s-endian.\n",
        is_big_endian() ? "big" : "little");

    return 0;
}

You also have this approach; from Quake II:

byte    swaptest[2] = {1,0};
if ( *(short *)swaptest == 1) {
    bigendien = false;

And !is_big_endian() is not 100% to be little as it can be mixed/middle.

Believe this can be checked using same approach only change value from 0x01000000 to i.e. 0x01020304 giving:

switch(e.c[0]) {
case 0x01: BIG
case 0x02: MIX
default: LITTLE

But not entirely sure about that one ...

User · Answer

The following will do   unsigned int x   1  printf    d    int     char    amp x  0       And setting  amp x to char   will enable you to access the individual bytes of the integer  and the ordering of bytes will depend on the endianness of the system

User · Answer

In short  yes   Suppose we are on a 32-bit machine   If it is little endian  the x in the memory will be something like          higher memory           ----- gt       ---- ---- ---- ----       0x01 0x00 0x00 0x00       ---- ---- ---- ----      A           amp x   so  char    amp x     1  and  y 48     1    If it is big endian  it will be        ---- ---- ---- ----       0x00 0x00 0x00 0x01       ---- ---- ---- ----      A           amp x   so this one will be  0

User · Answer

This is big endian test from a configure script    include  lt inttypes h gt  int main int argc  char    argv       volatile uint32 t i 0x01234567         return 0 for big endian  1 for little endian      return     uint8 t    amp i       0x67

[c] C program to check little vs. big endian

Examples related to c

Examples related to byte

Examples related to endianness