---
name: "memset"
section: "3"
platform: "linux"
package: "man-pages"
version: "6.19-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux", "freebsd", "macos"]
url: "https://new.carta.tech/memset"
---

# memset(3)

memory set

## 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)](/attributes/7.md).

| | | |
| --- | --- | --- |
| **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)](/memset_explicit/3.md).

## SEE ALSO

[**memory.h**(3head)](/memory.h/3head.md), [**bzero**(3)](/bzero/3.md), [**swab**(3)](/swab/3.md), [**wmemset**(3)](/wmemset/3.md)