This is a snippet to test a OS use which endian.

byteboder

#include<stdio.h>

int main(int argc, char *argv[])
{
    union 
    {
      short s;
      char c[sizeof(short)];
    }un;
    
    un.s = 0x0102;
    if(sizeof(short) == 2)
    {
      if(c[0] == 1 && c[1] == 2)
        printf("big-endia\n");
      else if(c[0] == 2 && c[1] == 1)
        printf("little-endian\n");
      else
        printf("unknow\n");
    }
    else
      printf("sizeof(short) = %d\n",sizeof(short));
      
    return 0;
}