a.c

#include <stdio.h>

typedef enum _endian {little_endian, big_endian} EndianType;
EndianType CheckCPUEndian() {
    unsigned short x;
    unsigned char c;
    EndianType CPUEndian;
    x = 0x0001;;
    c = *(unsigned char *)(&x);
    if( c == 0x01 )
        CPUEndian = little_endian;
    else
        CPUEndian = big_endian;
    return CPUEndian;
}

int main(int argc, char ** argv) {
  EndianType t = CheckCPUEndian();
  if (t == little_endian) {
    printf("Little endian\n");
  } else {
    printf("Big endian\n");
  }
}