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.