Chapter 3. Regular Expressions and Pattern Matching

There are hundreds of UNIX/Linux utilities available, and many of them are everyday commands such as ls, pwd, who, and vi. Just as there are essential tools that a carpenter uses, there are also essential tools the shell programmer needs to write meaningful and efficient scripts. The three major utilities that will be discussed in detail here are grep, sed, and awk. These programs are the most important UNIX/Linux tools available for manipulating text, output from a pipe, or standard input. In fact, sed and awk are often used as scripting languages by themselves. Before you fully appreciate the power of grep, sed, and awk, you must have a good foundation on the use of regular expressions and regular expression metacharacters. A complete list of useful UNIX/Linux utilities is found in Appendix A of this book.