A special case of a Unixfilter that reads its entIRe input before writing any output the canonical example is a sort utility. Unlike most filters, a sponge can conveniently overwrite the input file with the output data stream. If a file system has file versioning (as ITS did and VMS does now) the sponge/filter distinction loses its usefulness, because dIRecting filter output would just write a new version. See also slurp. [Jargon File] (1995-01-18)