Debra Cameron - Learning GNU Emacs, 3rd Edition

Stallman is widely recognized as the founder of the free software movement, which was an important predecessor of the open source movement. Linux is now the most prominent example of open source software, and it falls under the GNU Public License or GPL (available online at http://www.gnu.org/copyleft/gpl.html). Stallman argues that much of Linux outside the kernel itself is GNU software and so he refers to it as GNU/Linux. All controversies aside, Stallman's contribution to the open source movement cannot be overestimated. GNU software and open source software distributed under the GPL are a mainstay for developers and computer users all over the world.

The FSF was created precisely to distribute programs under terms that encourage you to share, rather than hoard, software. The GPL is designed to prevent an unfortunately common practice—namely, a company taking public domain code, making a few modifications and bug fixes, and then copyrighting the modified version. Once a company does this, the program has essentially become private property and disappears from the public domain. Stallman formed the foundation because he finds this practice abhorrent. As he explains in the GNU Manifesto, "I cannot in good conscience sign a nondisclosure agreement or a software license agreement . . . So that I can continue to use computers without dishonor, I have decided to put together a sufficient body of free software so that I will be able to get along without any software that is not free." Elsewhere in the manifesto, Stallman calls sharing software the "fundamental act of friendship among programmers." Their software is free because it can be shared and will always be shareable—without restriction. FSF software is not under restrictive copyright laws, which Stallman objects to in principle. In fact, he coined the term copyleft to describe the FSF's sharable software base. [3] FSF programs such as Emacs are often distributed with commercial systems. Even in these cases, the General Public License guarantees your right to use and give away their programs without restriction. Of course, the license does not apply to other proprietary software with which GNU tools have been shipped.

Since GNU Emacs was first released, many other pieces of the GNU operating environment have fallen into place: C and C++ compilers ( gcc and g++ ), a very powerful debugger ( gdb ), substitutes for lexand yacc(called flex and bison , respectively), a Unix shell ( bash , which stands for "Bourne-Again Shell"), the Gimp (a graphics tool comparable to Adobe PhotoShop), GNOME (a desktop environment for Linux), and many other programs and libraries. Many important open source projects that originally used variants of the GPL or other licensing schemes have adopted the GPL as their license, including Python, Mozilla, and Zope. Author David Wheeler argues that all open source projects should release their software under a GPL-compatible license [4] GPL-compatible is a critical distinction for many organizations. As our reviewer Mike Trent points out, many organizations release their software under a modified GPL because the GPL's license is actually "viral." That is, if one line of GPL'd code appears in a project, the entire project must be GPL'd. This means corporations interested in protecting their assets but still wanting to share code with the open source community cannot use the GPL without some modification. (see http://www.dwheeler.com/essays/gpl-compatible.html for his views and some statistics about GPL'd software). With Linux, GNU tools, and other GPL'd software, it's possible to have a complete operating environment consistent with the values set forth by the FSF.

This book is designed to get you started with Emacs as quickly as possible, whether you are an experienced computer user or a novice. The first two chapters give you the basics you need to know, and the rest of the book builds on these basics. After the first two chapters, you don't have to read the rest consecutively; you can skip to the topics that interest you. Additionally, the book is designed to give you just the level of hand-holding you want; you can either read the book in detail or skim it, looking for tables of commands and examples.

Here are some reading paths you could take:

These reading paths are offered only as a guideline. Emacs is one gigantic, functionally rich editor. We've divided it up into digestible bites for you, so you don't have to be put off by its size and scope. The best way to learn Emacs is incrementally; learn a little now, then learn more features as you get curious about them. If you need to do something and don't know how to do it in Emacs, Emacs probably already does it; if it doesn't, you can learn how to write a Lisp function to add it to Emacs (see Chapter 11for details). The online help system is an excellent place to learn about new features on the fly; online help is discussed in Chapter 1 Chapter 1. Emacs Basics Some of you out there are probably dying to get your hands on the keyboard and start typing. We won't try to stop you; turn to the section called "Starting Emacs" and you can go ahead. But do read the beginning of this chapter later when you're ready for a break. Emacs is much easier to learn if you understand some of the basic concepts involved, which we discuss in the following introduction. and in more detail in Chapter 14 Chapter 14. The Help System Emacs has the most comprehensive help facility of any text editor—and one of the best such facilities of any program at all. In fact, the Emacs help facilities probably cut down the time it took for us to write this book by an order of magnitude, and they can help you immeasurably in your ongoing quest to learn more about Emacs. In this chapter, we describe Emacs help in the following areas: • The tutorial. • The help key ( C-h ) and Help menu, which allow you to get help on a wide variety of topics. • The help facilities of complex commands like query-replace and dired . • Navigating Emacs manuals and using the info documentation reader. • Completion , in which Emacs helps you finish typing names of functions, variables, filenames, and more. Completion not only saves you time and helps you complete names of functions you know about but can help you discover new commands and variables. .