System Administration

Once you start using Ruby, youll want to use it everywhere. Well, nothings stopping you. This chapter shows you how to use Ruby in command-line programs that solve general everyday problems. It also demonstrates patterns that you can use to solve your own, more specific everyday problems.

System administration scripts are usually private scripts, disposable or lightly reusable. Ruby scripts are easy to write, so you can get the job done quickly and move on. You won feel bad if your script is less rigorous than your usual work, and you won feel invested in a huge program that you only needed once.

Rubys syntax makes it easy to write, but for system administration, its the libraries that make Ruby powerful. Most of the recipes in this chapter combine ideas from recipes elsewhere in the book to solve a real-world problem. The most commonly used idea is the Find.find technique first covered in Recipe 6.12. Recipes 23.5, 23.6, 23.7, 23.8, and 23.9 all give different twists on this technique.

The major new feature introduced in this chapter is Rubys standard etc library. It lets you query a Unix systems users and groups. Its used in Recipe 23.10 to look up a users ID given their username. Recipe 23.9 uses it to find a users home directory and to get the members of Unix groups.

Although these recipes focus mainly on Unix system administration, Ruby is perhaps even more useful for Windows administration. Unix has a wide variety of standard shell tools and an environment that makes it easy to combine them. If Ruby and other high-level languages didn exist, Unix administrators would still have tools like find and cut, and theyd use those tools like they did throughout the 1980s. On Windows, though, languages like Ruby are useful even for simple administration tasks: Ruby is easier to use than VBScript or batch files.

If you e trying to administer a Windows machine with Ruby, there are many third-party libraries that provide Ruby hooks into Windows internals: see especially the "win32utils" project at http://rubyforge.org/projects/win32utils/. Another useful library is Rubys standard Win32OLE library, which lets you do things like query Active Directory.

Libraries are also available for the more esoteric parts of Unix systems. See, for instance, Recipe 23.10, which uses the third-party library sys-proctable to gain access to the kernels process table.