| MEMCMP(3) | Library Functions Manual | MEMCMP(3) | 
memcmp —
#include <string.h>
int
  
  memcmp(const
    void *b1, const void
    *b2, size_t
  len);
memcmp() function compares byte string
  b1 against byte string b2. Both
  strings are assumed to be len bytes long.
memcmp() function returns zero if the two strings
  are identical, otherwise returns the difference between the first two
  differing bytes (treated as unsigned char values, so that
  ‘\200’ is greater than
  ‘\0’, for example). Zero-length strings
  are always identical.
Do not use memcmp() to compare
    cryptographic secrets, because the time it takes varies depending on how
    many bytes are the same, and thus leaks information about the two strings by
    a timing side channel. To compare secrets, hashes, message authentication
    codes, etc., use
    consttime_memequal(3)
    instead.
memcmp() function conforms to ANSI
  X3.159-1989 (“ANSI C89”).
| June 23, 2013 | NetBSD 9.3 |