complete system programs "the greps of wraththis wraps up our look at the system interfaces domain in python by presenting collection of larger python scripts that do real systems work--comparing and copying directory treessplitting filessearching files and directoriestesting other programsconfiguring launched programsshell environmentsand so on the examples here are python system utility programs that illustrate typical tasks and techniques in this domain and focus on applying built-in toolssuch as file and directory tree processing although the main point of this case-study is to give you feel for realistic scripts in actionthe size of these examples also gives us an opportunity to see python' support for development paradigms like object-oriented programming (oopand reuse at work it' really only in the context of nontrivial programs such as the ones we'll meet here that such tools begin to bear tangible fruit this also emphasizes the "whyof system toolsnot just the "how"along the wayi'll point out real-world needs met by the examples we'll studyto help you put the details in context one note up frontthis moves quicklyand few of its examples are largely listed just for independent study because all the scripts here are heavily documented and use python system tools described in the preceding won' go through all the code in exhaustive detail you should read the source code listings and experiment with these programs on your own computer to get better feel for how to combine system interfaces to accomplish realistic tasks all are available in source code form in the book' examples distribution and most work on all major platforms should also mention that most of these are programs have really usednot examples written just for this book they were coded over period of years and perform widely differing tasksso there is no obvious common thread to connect the dots here other than need on the other handthey help explain why system tools are useful in the first placedemonstrate larger development concepts that simpler examples cannotand bear collective witness to the simplicity and portability of automating system tasks with python once you've mastered the basicsyou'll wish you had done so sooner