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MEMCMP(3)		 BSD Library Functions Manual		     MEMCMP(3)

NAME
     memcmp -- compare byte string

LIBRARY
     Standard C	Library	(libc, -lc)

SYNOPSIS
     #include <string.h>

     int
     memcmp(const void *b1, const void *b2, size_t len);

DESCRIPTION
     The memcmp() function compares byte string	b1 against byte	string b2.
     Both strings are assumed to be len	bytes long.

RETURN VALUES
     The memcmp() function returns zero	if the two strings are identical, oth-
     erwise 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 in-
     formation about the two strings by	a timing side channel.	To compare se-
     crets, hashes, message authentication codes, etc.,	use
     consttime_memequal(3) instead.

SEE ALSO
     bcmp(3), consttime_memequal(3), strcasecmp(3), strcmp(3), strcoll(3),
     strxfrm(3)

STANDARDS
     The memcmp() function conforms to ANSI X3.159-1989	("ANSI C89").

BSD				 June 23, 2013				   BSD

NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUES | SEE ALSO | STANDARDS

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