man-pages/man2/umask.2

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.\" Hey Emacs! This file is -*- nroff -*- source.
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.\" Copyright (c) 1992 Drew Eckhardt (drew@cs.colorado.edu), March 28, 1992
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.\" Modified by Michael Haardt <michael@moria.de>
.\" Modified Sat Jul 24 12:51:53 1993 by Rik Faith <faith@cs.unc.edu>
.\" Modified Tue Oct 22 22:39:04 1996 by Eric S. Raymond <esr@thyrsus.com>
.\" Modified Thu May 1 06:05:54 UTC 1997 by Nicol<6F>s Lichtmaier
.\" <nick@debian.com> with Lars Wirzenius <liw@iki.fi> suggestion
.TH UMASK 2 1998-08-09 "Linux" "Linux Programmer's Manual"
.SH NAME
umask \- set file creation mask
.SH SYNOPSIS
.B #include <sys/types.h>
.br
.B #include <sys/stat.h>
.sp
.BI "mode_t umask(mode_t " mask );
.SH DESCRIPTION
.B umask
sets the umask to
.I mask
& 0777.
The umask is used by
.BR open (2)
to set initial file permissions on a newly-created file.
Specifically, permissions in the umask are turned off from
the \fBmode\fR argument to
.BR open (2)
(so, for example, the common umask default value of 022 results in new
files being created with permissions 0666 & ~022 = 0644 = rw-r--r--
in the usual case where the \fBmode\fR is specified as 0666).
.SH "RETURN VALUE"
This system call always succeeds and the previous value of the mask
is returned.
.SH "CONFORMING TO"
SVr4, SVID, POSIX, X/OPEN, BSD 4.3
.SH "SEE ALSO"
.BR creat (2),
.BR open (2)