The authors' approach to Unix security is holistic and clever; they devote as much space to security philosophy as to advice about closing TCP ports and disabling unnecessary services. They also recognize that lots of Unix machines are development platforms, and make many recommendations to consider as you design software. It's rare that you read a page in this carefully compiled book that does not impart some obscure nugget of knowledge, or remind you to implement some important policy. Plus, the authors have a style that reminds their readers that computing is supposed to be about intellectual exercise and fun, an attitude that's absent from too much of the information technology industry lately. Read this book if you use any flavor of Unix in any mission-critical situation. --David Wall

Topics covered: Security risks (and ways to limit them) under Linux, Solaris, Mac OS X, and FreeBSD. Coverage ranges from responsible system administration (including selection of usernames and logins) to intrusion detection, break-in forensics, and log analysis.

The first thing users of the Linux operating system come face to face with is the shell. "Shell" is the UNIX term for a user interface to the system -- something that lets you communicate with the computer via the keyboard and display. Bash, the Free Software Foundation's "Bourne Again Shell," is the default shell for Linux, the popular free UNIX-like operating system. It's also a replacement for the standard UNIX Bourne shell, which serves both as a user interface and as a programming language. Like the FSF's other tools, bash is more than a mere replacement: it extends the Bourne shell in many ways. Features include command line editing, key bindings, integrated programming features, command completion, control structures (especially the select construct, which enables you to create menus easily), and new ways to customize your environment.

Whether you want to use bash for its user interface or its programming features you will find Learning the bash Shell a valuable guide. The book covers all of bash's features, both for interactive use and programming. If you are new to shell programming, Learning the bash Shell provides an excellent introduction, covering everything from the most basic to the most advanced features, like signal handling and command line processing. If you've been writing shell scripts for years, it offers a great way to find out what the new shell offers. The book is full of examples of shell commands and programs that are designed to be useful in your everyday life as a user, not just to illustrate the feature being explained. All of these examples are freely available to you online on the Internet.