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memset(3) — Linux manual page

NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | ATTRIBUTES | STANDARDS | HISTORY | CAVEATS | SEE ALSO | COLOPHON 

memset(3)                Library Functions Manual               memset(3)

NAME         top

       memset - memory set

LIBRARY         top

       Standard C library (libc, -lc)

SYNOPSIS         top

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

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

DESCRIPTION         top

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

RETURN VALUE         top

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

ATTRIBUTES         top

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

STANDARDS         top

       C11, POSIX.1-2008.

HISTORY         top

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

CAVEATS         top

       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         top

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

COLOPHON         top

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

Pages that refer to this page: mount_setattr(2),  openat2(2),  set_thread_area(2),  bzero(3),  memory.h(3head),  memset_explicit(3),  NULL(3const),  size_t(3type),  void(3type),  wmemset(3),  aio(7),  feature_test_macros(7),  signal-safety(7)

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