Lesk wrote Unix tools for word processing (tbl, refer, and the standard ms macro package, all for troff), for compiling (Lex), and for networking (uucp).
He also wrote the Portable I/O Library (the predecessor to stdio.h in C) and contributed significantly to the development of the C language preprocessor.
[4] In 1984, he left to work for Bellcore, where he managed the computer science research group.
From 1998 to 2002, Lesk headed the National Science Foundation's Division of Information and Intelligent Systems, where he oversaw Phase 2 of the NSF's Digital Library Initiative.
[3][5][6] Lesk received the Flame award for lifetime achievement from Usenix in 1994, is a Fellow of the ACM in 1996,[1] and in 2005 was elected to the National Academy of Engineering.