UMASK(3)                   POSIX Programmer's Manual                  UMASK(3)



PROLOG
       This manual page is part of the POSIX Programmer's Manual.  The OS
       implementation of this interface may differ (consult the corresponding
       OS manual page for details of OS behavior), or the interface may not be
       implemented on OS.

NAME
       umask -- set and get the file mode creation mask

SYNOPSIS
       #include <sys/stat.h>

       mode_t umask(mode_t cmask);

DESCRIPTION
       The umask() function shall set the file mode creation mask of the
       process to cmask and return the previous value of the mask. Only the
       file permission bits of cmask (see <sys/stat.h>) are used; the meaning
       of the other bits is implementation-defined.

       The file mode creation mask of the process is used to turn off
       permission bits in the mode argument supplied during calls to the
       following functions:

        *  open(), openat(), creat(), mkdir(), mkdirat(), mkfifo(), and
           mkfifoat()

        *  mknod(), mknodat()

        *  mq__open()

        *  sem__open()

       Bit positions that are set in cmask are cleared in the mode of the
       created file.

RETURN VALUE
       The file permission bits in the value returned by umask() 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
       umask() with the returned value as cmask shall leave the state of the
       mask the same as its state before the first call, including any
       unspecified use of those bits.

ERRORS
       No errors are defined.

       The following sections are informative.

EXAMPLES
       None.

APPLICATION USAGE
       None.

RATIONALE
       Unsigned argument and return types for umask() were proposed. The
       return type and the argument were both changed to mode_t.

       Historical implementations have made use of additional bits in 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.1-2017.

FUTURE DIRECTIONS
       None.

SEE ALSO
       creat(), exec, mkdir(), mkfifo(), mknod(), mq__open(), open(),
       sem__open()

       The Base Definitions volume of POSIX.1-2017, <sys_stat.h>,
       <sys_types.h>

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1-2017, Standard for Information Technology --
       Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the
       Institute of Electrical and Electronics Engineers, Inc and The Open
       Group.  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.opengroup.org/unix/online.html .

       Any typographical or formatting errors that appear in this page are
       most likely to have been introduced during the conversion of the source
       files to man page format. To report such errors, see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .



IEEE/The Open Group                  2017                             UMASK(3)
