umask [ -S ] [ mask ]
The umask is set to mask. mask can be either an octal number or
a symbolic value as described in chmod(1). If mask is omitted,
the current value is printed. The -S option causes the mask to
be printed as a symbolic value. Otherwise, the mask is printed
as an octal number. Note that in the symbolic form the permis-
sions you specify are those which are to be allowed (not denied)
to the users specified.