Use the Power of Command Shells

Every woodworker needs a good, solid, reliable workbench, somewhere to hold work pieces at a convenient height while he or she works them. The workbench becomes the center of the wood shop, the craftsman returning to it time and time again as a piece takes shape.

For a programmer manipulating files of text, that workbench is the command shell. From the shell prompt, you can invoke your full repertoire of tools, using pipes to combine them in ways never dreamt of by their original developers. From the shell, you can launch applications, debuggers, browsers, editors, and utilities. You can search for files, query the status of the system, and filter output. And by programming the shell, you can build complex macro commands for activities you perform often.

For programmers raised on GUI interfaces and integrated development environments (IDEs), this might seem an extreme position. After all, can't you do everything equally well by pointing and clicking?

The simple answer is "no." GUI interfaces are wonderful, and they can be faster and more convenient for some simple operations. Moving files, reading MIME-encoded e-mail, and typing letters are all things that you might want to do in a graphical environment. But if you do all your work using GUIs, you are missing out on the full capabilities of your environment. You won't be able to automate common tasks, or use the full power of the tools available to you. And you won't be able to combine your tools to create customized macro tools. A benefit of GUIs is WYSIWYG—what you see is what you get. The disadvantage is WYSIAYG—what you see is all you get.

GUI environments are normally limited to the capabilities that their designers intended. If you need to go beyond the model the designer provided, you are usually out of luck—and more often than not, you do need to go beyond the model. Pragmatic Programmers don't just cut code, or develop object models, or write documentation, or automate the build process—we do all of these things. The scope of any one tool is usually limited to the tasks that the tool is expected to perform. For instance, suppose you need to integrate a code preprocessor (to implement design-by-contract, or multi-processing pragmas, or some such) into your IDE. Unless the designer of the IDE explicitly provided hooks for this capability, you can't do it.

You may already be comfortable working from the command prompt, in which case you can safely skip this section. Otherwise, you may need to be convinced that the shell is your friend.

As a Pragmatic Programmer, you will constantly want to perform ad hoc operations—things that the GUI may not support. The command line is better suited when you want to quickly combine a couple of commands to perform a query or some other task.

The Pragmatic Programmer: From Journeyman to Master

— by Andrew Hunt and David Thomas