-
-@item -d @var{var}[=@var{value}]
-@itemx --define=@var{var}[=@var{value}]
-
-Defines an `environment variable' named @var{var} having the optional
-value @var{value} specified. @xref{Variable values}.
-
-@item -u @var{var}
-@itemx --undef=@var{var}
-
-Undefines the `environment variable' named @var{var}. @xref{Variable
-values}.