man umask () - set and get the file mode creation mask
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 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.
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 IEEE Std 1003.1-2001.
FUTURE DIRECTIONS
None.
SEE ALSO
creat() , mkdir() , mkfifo() , open() , the Base Definitions volume of IEEE Std 1003.1-2001, <sys/stat.h>, <sys/types.h>
COPYRIGHT
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 original Standard can be obtained online at http://www.opengroup.org/unix/online.html .