The
umask();
routine sets the process's file mode creation mask to
numask
and returns the previous value of the mask.
The 9 low-order access permission bits of
numask
are used by system calls, including
open(2),
mkdir(2),
mkfifo(2)
and
mknod(2)
to turn off corresponding bits requested in the file mode
(see
chmod(2/)).
This clearing allows each user to restrict the default access to his files.
The default mask value is S_IWGRP|S_IWOTH (022, write access for the
owner only).
Child processes inherit the mask of the calling process.
RETURN VALUES
The previous value of the file mode mask is returned by the call.