Additional information
by Chris Johnson (Author)
Introduction Although most users think of the shell as an interactive command interpreter, it is really a programming language in which each statement runs a command. Because it must satisfy both the interactive and programming aspects of command execution, it is a strange language, shaped as much by history as by design. Brian Kernighan and Rob Pike, The UNIX Programming Environment, Prentice-Hall, 1984 The shell is a programming language. Don't let anyone tell you otherwise. The shell is not just glue that sticks bits together. The shell is a lot more than a tool that runs other tools. The shell is a complete programming language! When a Linux user asked me about membership databases, I asked him what he really needed. He wanted to store names and addresses for a couple of hundred members and print mailing labels for each of them. I recommended using a text editor to store the information in a text file, and I provided a shell script to create the labels in PostScript. (The script, ps-labels, appeared in my first book, Shell Scripting Recipes: A Problem-Solution Approach. ) When the SWEN worm was dumping hundreds of megabytes of junk into my mailbox every few minutes, I wrote a shell script to filter them out on the mail server and download the remaining mail to my home computer. That script has been doing its job for several years.
Author Biography
Chris F.A. Johnson was introduced to Unix in 1990 and learned shell scripting because there was no C compiler on the system. His first major project was a menu-driven, user-extensible database system with report generator. Chris uses the shell as his primary, general-purpose programming language, and his projects have included a member database, menuing system, and POP3 mail filtering and retrieval. Chris is the author of Shell Scripting Recipes: A Problem-Solution Approach (Apress, 2005). When not pushing shell scripting to the limit, he designs and codes web sites, teaches chess, and composes cryptic crosswords.
