'\" t
.\" Copyright 1993, David Metcalfe <david@prism.demon.co.uk>
.\" Copyright, the authors of the Linux man-pages project
.\"
.\" SPDX-License-Identifier: Linux-man-pages-copyleft
.\"
.TH memset 3 2026-08-10 "Linux man-pages 6.19"
.SH NAME
memset \- memory set
.SH LIBRARY
Standard C library
.RI ( libc ,\~ \-lc )
.SH SYNOPSIS
.nf
.BR #include\~<string.h> "  // see memory.h(3head)"
.P
.BR "void *memset(" "size_t n;"
.BI "             void " a [ n "], int " c ", size_t " n );
.fi
.SH DESCRIPTION
The
.BR memset ()
function fills the first
.I n
bytes of the
memory area pointed to by
.I a
with the constant byte
.IR c .
.SH RETURN VALUE
The
.BR memset ()
function returns a pointer to the memory area
.IR a .
.SH ATTRIBUTES
For an explanation of the terms used in this section, see
.BR attributes (7).
.TS
allbox;
lbx lb lb
l l l.
Interface	Attribute	Value
T{
.na
.nh
.BR memset ()
T}	Thread safety	MT-Safe
.TE
.SH STANDARDS
C11, POSIX.1-2008.
.SH HISTORY
POSIX.1-2001, C89, SVr4, 4.3BSD.
.SH 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
.BR memset_explicit (3).
.SH SEE ALSO
.BR memory.h (3head),
.BR bzero (3),
.BR swab (3),
.BR wmemset (3)