[Qt-interest] How can I use the system envoriment variable in qt project file(.pro) ?

[Jochen Roemmler]

>   How can I use the Linux system variable such as $PATH $QTDIR in .pro
> file ?
>   For example, I want to use:
>   LIBS += -L$QTDIR/lib -lgui
> 
> I want the compiler use argument "-L/opt/qt/lib -lgui" where
> $QTDIR=/opt/qt

LIBS += -L$$(QTDIR)/lib -lgui

perhaps?