Pro Bash Programming: Scripting the GNU/Linux Shell

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Автор: Chris F.A. Johnson

Название: Pro Bash Programming: Scripting the GNU/Linux Shell

Издательство: Apress

Год: 2009

Формат: PDF

Размер: 5.2 Mb

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.

I used to tell people that I did most of my programming in the shell but switched to C for anything that needed the extra speed. It has been several years since I have needed to use C, so I no longer mention it. I do everything in the shell.

A shell script is as much a program as anything written in C, Python, or any other language. Just

because shell scripts are easier to write doesn’t mean they should take a backseat to compiled programs or other scripting languages. I use the terms script and program interchangeably when referring to tasks written in the shell.