Determining CPU endianness at runtime

Since the short 1 is represented as 00 00 00 01 on big endian machines and 01 00 00 00 on little endian machines, it's a rather straight forward matter to detect the endianness of a machine, by simply looking at how it stores a short.

#include <stdio.h>

int main() {
    unsigned short i = 1; // store a short
    char* p = (char*) &i; // convert the short into an array of bytes

    if (p[0] == 1) {
        // if the first byte is 01, then it's a little endian machine
        printf("Little endian\n");
    } else {
        // otherwise, it's a big endian machine
        printf("Big endian\n");
    }

    return 0;
}