.\"	$OpenBSD: umask.2,v 1.10 2013/07/17 05:42:11 schwarze Exp $
.\"	$NetBSD: umask.2,v 1.6 1995/02/27 12:39:06 cgd Exp $
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.\"     @(#)umask.2	8.1 (Berkeley) 6/4/93
.\"
.Dd $Mdocdate: July 17 2013 $
.Dt UMASK 2
.Os
.Sh NAME
.Nm umask
.Nd set file creation mode mask
.Sh SYNOPSIS
.Fd #include <sys/types.h>
.Fd #include <sys/stat.h>
.Ft mode_t
.Fn umask "mode_t numask"
.Sh DESCRIPTION
The
.Fn umask
routine sets the process's file mode creation mask to
.Fa numask
and returns the previous value of the mask.
The 9 low-order access permission bits of
.Fa numask
are used by system calls, including
.Xr open 2 ,
.Xr mkdir 2 ,
.Xr mkfifo 2
and
.Xr mknod 2
to turn off corresponding bits requested in the file mode
(see
.Xr chmod 2 ) .
This clearing allows each user to restrict the default access to his files.
.Pp
The default mask value is S_IWGRP|S_IWOTH (022, write access for the
owner only).
Child processes inherit the mask of the calling process.
.Sh RETURN VALUES
The previous value of the file mode mask is returned by the call.
.Sh ERRORS
The
.Fn umask
function is always successful.
.Sh SEE ALSO
.Xr chmod 2 ,
.Xr mkdir 2 ,
.Xr mkfifo 2 ,
.Xr mknod 2 ,
.Xr open 2
.Sh STANDARDS
The
.Fn umask
function conforms to
.St -p1003.1-2008 .
.Sh HISTORY
The
.Fn umask
system call first appeared in
.At v7 .