memset(3)                  Library Functions Manual                  memset(3)

NAME
       memset - memory set

LIBRARY
       Standard C library (libc, -lc)

SYNOPSIS
       #include <string.h>  // see memory.h(3head)

       void *memset(size_t n;
                    void a[n], int c, size_t n);

DESCRIPTION
       The memset() function fills the first n bytes of the memory area
       pointed to by a with the constant byte c.

RETURN VALUE
       The memset() function returns a pointer to the memory area a.

ATTRIBUTES
       For an explanation of the terms used in this section, see
       attributes(7).

       +--------------------------------------------+---------------+---------+
       |Interface                                   | Attribute     | Value   |
       +--------------------------------------------+---------------+---------+
       |memset ()                                   | Thread safety | MT-Safe |
       +--------------------------------------------+---------------+---------+
STANDARDS
       C11, POSIX.1-2008.

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

CAVEATS
       If the compiler deduces that the operation is unnecessary, it may
       totally or partially remove the call.  To ensure the setting happens
       regardless of optimizations, use memset_explicit(3).

SEE ALSO
       memory.h(3head), bzero(3), swab(3), wmemset(3)

Linux man-pages 6.19              2026-08-10                         memset(3)