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memcmp(3)               Library Functions Manual               memcmp(3)

ИМЯ

       memcmp - compare memory areas

БИБЛИОТЕКА

       Standard C library (libc, -lc)

СИНТАКСИС

       #include <string.h>

       int memcmp(const void s1[.n], const void s2[.n], size_t n);

ОПИСАНИЕ

       The memcmp() function compares the first n bytes (each
       interpreted as unsigned char) of the memory areas s1 and s2.

ЗНАЧЕНИЕ, ВОЗВРАЩАЕМОЕ ФУНКЦИЕЙ

       The memcmp() function returns an integer less than, equal to, or
       greater than zero if the first n bytes of s1 is found,
       respectively, to be less than, to match, or be greater than the
       first n bytes of s2.

       For a nonzero return value, the sign is determined by the sign of
       the difference between the first pair of bytes (interpreted as
       unsigned char) that differ in s1 and s2.

       If n is zero, the return value is zero.

АТРИБУТЫ

       For an explanation of the terms used in this section, see
       attributes(7).
       ┌─────────────────────────────────────┬───────────────┬─────────┐
       │ Interface                           │ Attribute     │ Value   │
       ├─────────────────────────────────────┼───────────────┼─────────┤
       │ memcmp()                            │ Thread safety │ MT-Safe │
       └─────────────────────────────────────┴───────────────┴─────────┘

СТАНДАРТЫ

       C11, POSIX.1-2008.

ИСТОРИЯ

       POSIX.1-2001, C89, SVr4, 4.3BSD.

ЗАМЕЧАНИЯ

       Do not use memcmp() to compare confidential data, such as
       cryptographic secrets, because the CPU time required for the
       comparison depends on the contents of the addresses compared,
       this function is subject to timing-based side-channel attacks.
       In such cases, a function that performs comparisons in
       deterministic time, depending only on n (the quantity of bytes
       compared) is required.  Some operating systems provide such a
       function (e.g., NetBSD's consttime_memequal()), but no such
       function is specified in POSIX.  On Linux, you may need to
       implement such a function yourself.

СМОТРИТЕ ТАКЖЕ

       bstring(3), strcasecmp(3), strcmp(3), strcoll(3), strncasecmp(3),
       strncmp(3), wmemcmp(3)

КОЛОФОН

       This page is part of the man-pages (Linux kernel and C library
       user-space interface documentation) project.  Information about
       the project can be found at 
       ⟨https://www.kernel.org/doc/man-pages/⟩.  If you have a bug report
       for this manual page, see
       ⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
       This page was obtained from the tarball man-pages-6.9.1.tar.gz
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       ⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on
       2024-06-26.  If you discover any rendering problems in this HTML
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       man-pages@man7.org

Linux man-pages 6.9.1          2024-05-02                      memcmp(3)

Страницы, которые ссылаются на эту страницу: bcmp(3), bstring(3), size_t(3type), strcasecmp(3), strcmp(3), strcoll(3), strxfrm(3), void(3type), wmemcmp(3), signal-safety(7)