UMASK(P) POSIX Programmer's Manual UMASK(P)
umask - set and get the file mode creation mask
mode_t umask(mode_t cmask);
The umask() function shall set the process' file mode creation mask 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 process' file mode creation mask is used during open(), creat(), mkdir(), and mkfifo()
to turn off permission bits in the mode argument supplied. Bit positions that are set in
cmask are cleared in the mode of the created file.
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.
No errors are defined.
The following sections are informative.
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 implementa-
tion-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
IEEE Std 1003.1-2001.
creat() , mkdir() , mkfifo() , open() , the Base Definitions volume of
IEEE Std 1003.1-2001, <sys/stat.h>, <sys/types.h>
Portions of this text are reprinted and reproduced in electronic form from IEEE Std
1003.1, 2003 Edition, Standard for Information Technology -- Portable Operating System
Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 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 orig-
inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .
IEEE/The Open Group 2003 UMASK(P)