  We consider systems of conservation laws endowed with a convex entropy. We
show the contraction, up to a translation, to extremal entropic shocks, for a
pseudo-distance based on the notion of relative entropy. The contraction holds
for bounded entropic weak solutions having an additional trace property. The
pseudo-distance depends only on the fixed extremal entropic shocks in play. In
particular, it can be chosen uniformly for any entropic weak solutions which
are compared to a fixed shock. The boundedness of the solutions controls the
strength of the shift needed to get the contraction. However, no $BV$ estimate
is needed on the weak solutions considered. The theory holds without smallness
condition. For fluid mechanics, the theory handles solutions with vacuum.
