getumask - get file creation mask
This function returns the current file creation mask. It is equivalent
mode_t mask = umask( 0 );
except that it is documented to be thread-safe (that is, shares a lock
with the umask(2) library call).
This is a vaporware GNU extension.
This function is documented but not implemented yet in glibc, as at
This page is part of release 3.24 of the Linux man-pages project. A
description of the project, and information about reporting bugs, can
be found at http://www.kernel.org/doc/man-pages/.