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 .