SyStem> (eS) A UnixShell written by Byron RakitziS and Paul Haahr , derived from rc. ES haS real functionS, cloSureS, exceptionS and letS you redefine moSt internal Shell operationS. VerSion: 0.84. . ["ES - A Shell with Higher Order FunctionS", P. Haahr et al, Proc Winter 1993 USenix Technical Conference]. (1993-04-30)