ufed - Gentoo Linux USE flags editor
What are USE flags?
The USE settings system is a flexible way to enable or disable various features at package build-time on a global level and for individual packages. This allows an administrator control over how packages are built in regards to the optional features which can be compiled into those packages. For instance, packages with optional GNOME support can have this support disabled at compile time by disabling the "gnome" USE setting. Enabling the "gnome" USE setting would enable GNOME sup- port in these same packages. The effect of USE settings on packages is dependent on whether both the software itself and the package ebuild supports the USE setting as an optional feature. If the software does not have support for an optional feature then the corresponding USE set- ting will obviously have no effect. Also many package dependencies are not considered optional by the software and thus USE settings will have no effect on those mandatory dependencies.