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.TH UMASK "3P" 2013 "IEEE/The Open Group" "POSIX Programmer's Manual"
.SH PROLOG
This manual page is part of the POSIX Programmer's Manual.
The Linux implementation of this interface may differ (consult
the corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.

.SH NAME
umask
\(em set and get the file mode creation mask
.SH SYNOPSIS
.LP
.nf
#include <sys/stat.h>
.P
mode_t umask(mode_t \fIcmask\fP);
.fi
.SH DESCRIPTION
The
\fIumask\fR()
function shall set the file mode creation mask of the process to
.IR cmask
and return the previous value of the mask. Only the file permission
bits of
.IR cmask
(see
.IR <sys/stat.h> )
are used; the meaning of the other bits is implementation-defined.
.P
The file mode creation mask of the process is used to turn off
permission bits in the
.IR mode
argument supplied during calls to the following functions:
.IP " *" 4
\fIopen\fR(),
\fIopenat\fR(),
\fIcreat\fR(),
\fImkdir\fR(),
\fImkdirat\fR(),
\fImkfifo\fR(),
and
\fImkfifoat\fR()
.IP " *" 4
\fImknod\fR(),
\fImknodat\fR()
.IP " *" 4
\fImq_open\fR()
.IP " *" 4
\fIsem_open\fR()
.P
Bit positions that are set in
.IR cmask
are cleared in the mode of the created file.
.SH "RETURN VALUE"
The file permission bits in the value returned by
\fIumask\fR()
shall be the previous value of the file mode creation mask. The state
of any other bits in that value is unspecified, except that a
subsequent call to
\fIumask\fR()
with the returned value as
.IR cmask
shall leave the state of the mask the same as its state before the
first call, including any unspecified use of those bits.
.SH ERRORS
No errors are defined.
.LP
.IR "The following sections are informative."
.SH EXAMPLES
None.
.SH "APPLICATION USAGE"
None.
.SH RATIONALE
Unsigned argument and return types for
\fIumask\fR()
were proposed. The return type and the argument were both changed to
.BR mode_t .
.P
Historical implementations have made use of additional bits in
.IR cmask
for their implementation-defined purposes. The addition of the text
that the meaning of other bits of the field is implementation-defined
permits these implementations to conform to this volume of POSIX.1\(hy2008.
.SH "FUTURE DIRECTIONS"
None.
.SH "SEE ALSO"
.IR "\fIcreat\fR\^(\|)",
.IR "\fIexec\fR\^",
.IR "\fImkdir\fR\^(\|)",
.IR "\fImkfifo\fR\^(\|)",
.IR "\fImknod\fR\^(\|)",
.IR "\fImq_open\fR\^(\|)",
.IR "\fIopen\fR\^(\|)",
.IR "\fIsem_open\fR\^(\|)"
.P
The Base Definitions volume of POSIX.1\(hy2008,
.IR "\fB<sys_stat.h>\fP",
.IR "\fB<sys_types.h>\fP"
.SH COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, Copyright (C) 2013 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group.
(This is POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online at
http://www.unix.org/online.html .

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