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.

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 .