The Heirloom Development Tools provide yacc, lex, m4, make, and SCCS as portable derivatives of the utilities released by Sun as part of OpenSolaris. The OpenSolaris utilities were in turn derived from the original Unix versions, and are assumed be conforming implementations of the POSIX standard.
OpenGrok is a fast and usable source code search and cross reference engine. It helps you search, cross-reference, and navigate your source tree. It can understand various program file formats and version control histories like Mercurial, Bazaar, Git, ClearCase, Perforce, SCCS, RCS, CVS, or Subversion. In other words, it lets you grok (profoundly understand) the source.