1 .\" Copyright (c) 2006, 2008, Michael Kerrisk (mtk.manpages@gmail.com)
2 .\" (A few fragments remain from an earlier (1992) version written in
3 .\" 1992 by Drew Eckhardt <drew@cs.colorado.edu>.)
5 .\" %%%LICENSE_START(VERBATIM)
6 .\" Permission is granted to make and distribute verbatim copies of this
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10 .\" Permission is granted to copy and distribute modified versions of this
11 .\" manual under the conditions for verbatim copying, provided that the
12 .\" entire resulting derived work is distributed under the terms of a
13 .\" permission notice identical to this one.
15 .\" Since the Linux kernel and libraries are constantly changing, this
16 .\" manual page may be incorrect or out-of-date. The author(s) assume no
17 .\" responsibility for errors or omissions, or for damages resulting from
18 .\" the use of the information contained herein. The author(s) may not
19 .\" have taken the same level of care in the production of this manual,
20 .\" which is licensed free of charge, as they might when working
23 .\" Formatted or processed versions of this manual, if unaccompanied by
24 .\" the source, must acknowledge the copyright and authors of this work.
27 .\" Modified by Michael Haardt <michael@moria.de>
28 .\" Modified Sat Jul 24 12:51:53 1993 by Rik Faith <faith@cs.unc.edu>
29 .\" Modified Tue Oct 22 22:39:04 1996 by Eric S. Raymond <esr@thyrsus.com>
30 .\" Modified Thu May 1 06:05:54 UTC 1997 by Nicolás Lichtmaier
31 .\" <nick@debian.com> with Lars Wirzenius <liw@iki.fi> suggestion
32 .\" 2006-05-13, mtk, substantial rewrite of description of 'mask'
33 .\" 2008-01-09, mtk, a few rewrites and additions.
34 .TH UMASK 2 2008-01-09 "Linux" "Linux Programmer's Manual"
36 umask \- set file mode creation mask
38 .B #include <sys/types.h>
40 .B #include <sys/stat.h>
42 .BI "mode_t umask(mode_t " mask );
45 sets the calling process's file mode creation mask (umask) to
47 & 0777 (i.e., only the file permission bits of
49 are used), and returns the previous value of the mask.
54 and other system calls that create files
55 .\" e.g., mkfifo(), creat(), mknod(), sem_open(), mq_open(), shm_open()
56 .\" but NOT the System V IPC *get() calls
57 to modify the permissions placed on newly created files or directories.
58 Specifically, permissions in the umask are turned off from
66 The constants that should be used to specify
71 The typical default value for the process umask is
72 .I S_IWGRP\ |\ S_IWOTH
74 In the usual case where the
81 S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH
84 (octal 0666) when creating a new file, the permissions on the
85 resulting file will be:
88 S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH
91 (because 0666 & ~022 = 0644; i.e., rw\-r\-\-r\-\-).
93 This system call always succeeds and the previous value of the mask
96 SVr4, 4.3BSD, POSIX.1-2001.
98 A child process created via
100 inherits its parent's umask.
101 The umask is left unchanged by
104 The umask setting also affects the permissions assigned to POSIX IPC objects
110 and UNIX domain sockets
112 created by the process.
113 The umask does not affect the permissions assigned
114 to System\ V IPC objects created by the process (using
125 This page is part of release 3.67 of the Linux
128 A description of the project,
129 information about reporting bugs,
130 and the latest version of this page,
132 \%http://www.kernel.org/doc/man\-pages/.