A special case of a Unixfilter that reads its entire input before writing any outputthe 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)