Question 20.9

comp.lang.c FAQ list · Question 20.9

Q: How can I determine whether a machine's byte order is big-endian or little-endian?

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A: The usual techniques are to use a pointer:

int x = 1;
 if(*(char *)&x == 1)
  printf("little-endian\n");
 else printf("big-endian\n");

or a union:

union {
  int i;
  char c[sizeof(int)];
 } x;
 x.i = 1;
 if(x.c[0] == 1)
  printf("little-endian\n");
 else printf("big-endian\n");

(Note that there are also byte order possibilities beyond simple big-endian and little-endian[footnote] .)
See also questions 10.16 and 20.9b.
References: H&S Sec. 6.1.2 pp. 163-4