UMASK(3P)

💅 UMASK(3P) — POSIX Programmer's Manual, bestie edition 🎀

okay so real talk first 🫶 this page lives in the POSIX Programmer's Manual, and the Linux implementation of this interface may differ (so like, go consult the corresponding Linux manual page for the details of Linux behavior, fr), or honestly the interface may not even be implemented on Linux. just so you know.

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✨ NAME ✨

umask — set and get the file mode creation mask. she's giving gatekeeper energy, but for permissions 💅

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🌸 SYNOPSIS 🌸

#include <sys/stat.h>

mode_t umask(mode_t cmask);

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💖 DESCRIPTION 💖

The umask() function shall set the file mode creation mask of the process to cmask and return the previous value of the mask. no cap, that's literally the whole job.

Only the file permission bits of cmask (peep <sys/stat.h>) are used; the meaning of the other bits is implementation-defined. so the extra bits are... vibes. implementation vibes. 🙈

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. it's giving "not on my watch" 💀

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👑 RETURN VALUE 👑

The file permission bits in the value returned by umask() shall be the previous value of the file mode creation mask. iconic. 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. so like... round-trip safe, periodt.

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🦋 ERRORS 🦋

No errors are defined. not a single one. she's unbothered. 🌈

The following sections are informative.

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🍓 EXAMPLES 🍓

None. (yeah, truly nothing. empty. blank. a clean slate bestie 💜)

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🧚 APPLICATION USAGE 🧚

None.

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💀 RATIONALE 💀

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

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. so the chaos was, like, grandfathered in. 💅

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⭐ FUTURE DIRECTIONS ⭐

None.

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🔥 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>

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🎀 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 .

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ok that's the whole thing, you ate that 💖

and that's a wrap bestie — this page is brought to you by IEEE/The Open Group, 2017, UMASK(3P). go forth and mask responsibly 🌸✨