---
name: "setmode"
section: "3"
platform: "freebsd"
package: "base"
version: "16.0-CURRENT-20261027-61c70dc16a79"
release: "FreeBSD 16.0-CURRENT (2026-10-27)"
platforms: ["linux", "freebsd", "macos"]
url: "https://new.carta.tech/getmode"
---

# setmode(3)

modify mode bits

Part of [getmode(3)](/getmode/3.md).

## NAME

**getmode**, **setmode** – modify mode bits

## LIBRARY

Standard C Library (libc, -lc)

## SYNOPSIS

**#include \<unistd.h\>**

*mode\_t*\

**getmode**(*const void \*set*, *mode\_t mode*);

*void* *\**\

**setmode**(*const char \*mode\_str*);

## DESCRIPTION

The **getmode**() function returns a copy of the file permission bits *mode* as altered by the values pointed to by *set*. While only the mode bits are altered, other parts of the file mode may be examined.

The **setmode**() function takes an absolute (octal) or symbolic value, as described in [chmod(1)](/chmod/1.md), as an argument and returns a pointer to mode values to be supplied to **getmode**(). Because some of the symbolic values are relative to the file creation mask, **setmode**() may call [umask(2)](/umask/2.md). If this occurs, the file creation mask will be restored before **setmode**() returns. If the calling program changes the value of its file creation mask after calling **setmode**(), **setmode**() must be called again if **getmode**() is to modify future file modes correctly.

If the mode passed to **setmode**() is invalid or if memory cannot be allocated for the return value, **setmode**() returns NULL.

The value returned from **setmode**() is obtained from **malloc**() and should be returned to the system with **free**() when the program is done with it, generally after a call to **getmode**().

## ERRORS

The **setmode**() function may fail and set errno for any of the errors specified for the library routine [malloc(3)](/malloc/3.md) or [strtol(3)](/strtol/3.md). In addition, **setmode**() will fail and set *errno* to:

- \[EINVAL\]

  The *mode* argument does not represent a valid mode.

## SEE ALSO

[chmod(1)](/chmod/1.md), [stat(2)](/stat/2.md), [umask(2)](/umask/2.md), [malloc(3)](/malloc/3.md)

## HISTORY

The **getmode**() and **setmode**() functions first appeared in 4.4BSD.

## BUGS

The **setmode**() function is not thread safe. Files created in other threads while **setmode**() is being called may be created with a umask of 0.