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Title: memset(3) - Linux manual page Authors: Venue: man Year: 2008 Canonical: man:man3/memset.3 URL: https://man7.org/linux/man-pages/man3/memset.3.html Collector: man OA: true ABSTRACT memset(3) - Linux manual page man7.org Linux man-pages Linux/UNIX system programming training 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 // 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 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-6.19.tar.gz fetched from ⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on 2026-09-09. If you discover any rendering problems in this HTML version of the page, or you believe there is a better or more up- to-date source for the page, or you have corrections or improvements to the information in this COLOPHON (which is not part of the original manual page), send a mail to man-pages@man7.org 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) HTML rendering created 2026-09-09 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH.