1UMASK(3P)                  POSIX Programmer's Manual                 UMASK(3P)
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PROLOG

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

12       umask — set and get the file mode creation mask
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SYNOPSIS

15       #include <sys/stat.h>
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17       mode_t umask(mode_t cmask);
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DESCRIPTION

20       The umask() function shall set the  file  mode  creation  mask  of  the
21       process  to  cmask  and return the previous value of the mask. Only the
22       file permission bits of cmask (see <sys/stat.h>) are used; the  meaning
23       of the other bits is implementation-defined.
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25       The  file mode creation mask of the process is used to turn off permis‐
26       sion bits in the mode argument supplied during calls to  the  following
27       functions:
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29        *  open(),  openat(), creat(), mkdir(), mkdirat(), mkfifo(), and mkfi‐
30           foat()
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32        *  mknod(), mknodat()
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34        *  mq_open()
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36        *  sem_open()
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38       Bit positions that are set in cmask are cleared in the mode of the cre‐
39       ated file.
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RETURN VALUE

42       The  file permission bits in the value returned by umask() shall be the
43       previous value of the file mode creation mask. The state of  any  other
44       bits  in  that  value  is unspecified, except that a subsequent call to
45       umask() with the returned value as cmask shall leave the state  of  the
46       mask the same as its state before the first call, including any unspec‐
47       ified use of those bits.
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ERRORS

50       No errors are defined.
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52       The following sections are informative.
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EXAMPLES

55       None.
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APPLICATION USAGE

58       None.
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RATIONALE

61       Unsigned argument and return  types  for  umask()  were  proposed.  The
62       return type and the argument were both changed to mode_t.
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64       Historical  implementations  have  made use of additional bits in cmask
65       for their implementation-defined purposes. The  addition  of  the  text
66       that  the  meaning of other bits of the field is implementation-defined
67       permits  these  implementations  to   conform   to   this   volume   of
68       POSIX.1‐2017.
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FUTURE DIRECTIONS

71       None.
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SEE ALSO

74       creat(),   exec,   mkdir(),   mkfifo(),   mknod(),  mq_open(),  open(),
75       sem_open()
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77       The   Base   Definitions   volume   of   POSIX.1‐2017,    <sys_stat.h>,
78       <sys_types.h>
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81       Portions  of  this text are reprinted and reproduced in electronic form
82       from IEEE Std 1003.1-2017, Standard for Information Technology --  Por‐
83       table  Operating System Interface (POSIX), The Open Group Base Specifi‐
84       cations Issue 7, 2018 Edition, Copyright (C) 2018 by the  Institute  of
85       Electrical  and  Electronics Engineers, Inc and The Open Group.  In the
86       event of any discrepancy between this version and the original IEEE and
87       The  Open Group Standard, the original IEEE and The Open Group Standard
88       is the referee document. The original Standard can be  obtained  online
89       at http://www.opengroup.org/unix/online.html .
90
91       Any  typographical  or  formatting  errors that appear in this page are
92       most likely to have been introduced during the conversion of the source
93       files  to  man page format. To report such errors, see https://www.ker‐
94       nel.org/doc/man-pages/reporting_bugs.html .
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98IEEE/The Open Group                  2017                            UMASK(3P)
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