memset(3) Library Functions Manual memset(3)

memset - memory set

Standard C library (libc-lc)

#include <string.h>  // see memory.h(3head)
void *memset(size_t n;
             void a[n], int c, size_t n);

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

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

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

Interface Attribute Value
memset () Thread safety MT-Safe

C11, POSIX.1-2008.

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

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).

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

2026-08-10 Linux man-pages 6.19