The cost of the extra lookups goes away entirely if one then extends the design in the ways already discussed elsewhere on this very page. Instead of the pipel

The cost of the extra lookups goes away entirely if one then extends the design in the ways already discussed elsewhere on this very page. Instead of the pipeline passing along a stream of bytes, which every program then parses into a stream of filenames, the pipeline passes along a stream of objects. Then "sort" becomes a utility that sorts a stream of objects by a chosen set of fields; "slash" becomes a utility that inspects the "file type" and "file name" field of an object and makes an appropriate "display name" field; and "ls" becomes a utility that outputs a stream of objects that have "file type" and "file name" fields, straight out of the directory entry. "ls" is the only part of the pipeline that looks at the disc.