The work distribution function for a non-relativistic, non-interacting quantum many-body system inter-acting with classical external sources is investigated. Exact expressions for the characteristic function corresponding to the work distribution function is obtained for arbitrary switching function and coupling functions. The many-body frequencies are assumed to be generally time-dependent in order to take into account the possibility of moving the boundaries of the system in a predefined process linking the char-acteristic function to the fluctuation-induced energies in confined geometries. Some limiting cases are considered and discussed.
