确定主机字节序

#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 (un.c[0] == 1 && un.c[1] == 2)
            printf("big-endian\n");
        else if (un.c[0] == 2 && un.c[1] == 1)
            printf("little-endian\n");
        else
            printf("unknown\n");
    } else
        printf("sizeof(short) = %d\n", sizeof(short));

    return 0;
}