$ gcc hello.m -o hello -I /GNUstep/System/Library/Headers -L /GNUStep/System/Library/Libraries/ -l objc gcc Sample01.m -o Sample01 -I /GNUstep/System/Library/Headers -L /GNUstep/System/Library/Libraries -lobjc -lgnustep-base -fconstant-string-class=NSConstantString -enable-auto-import