Last summer I was looking for a program that would tell me which shell commands last used in a specific directory. Because I had been reading "The Unix Programming Environment" it quickly occurred to me that the program I was looking for could easily be made from several existing commands. Only after I wrote the small script did I find that the solution already existed except it was >1000 lines of code, 20 github contributors, and utilized a sqlite database.

My one line has less features, but I'll take it.