Emacs: Editing, Writing and Programming

Transcription

1 Emacs: Editing, Writing and Programming KOM Computer Workshop Release 1.20 September 30, Introduction Editing of text is probably one the functions you will need the most from the UNIX system. Lots of different programs exist for performing this exact task - some easier to use than others. And some more versatile than others. Starting with the simple tools, one could mention the text-based pico which uses the same editing facilities as found in the pine mail reader. A series of attempts to copy the Windows Word(pad) also exists - such as gedit, nedit, etc. These are self-explanatory and doesn t really offer much in the area of versatility. Instead lets get down to business and make clear once and for all that the FSF GNU Emacs is the way to go when editing your Latex report, source code, system files, etc. Many users stall the first time they re presented with the Emacs user interface - the shortcut keys are not the same as seen in Microsoft environments and it is not WYSIWYG. However - what is not apperant at first sight is the incredible versatility you will learn to appreciate. Among the neatest features one can mention: Syntax highlighting - makes your source code a lot easier to read and edit. Keyboard shourtcuts for everything - give your mouse a rest and save yourselves from straining your hands. Total integration with the Latex document writing system and version control. Total lack of annoying Office assistants, auto correct facilities and other functions for aiding dumb users :-) You may at first not believe that emacs is that great a program - nevertheless, experience shows that nearly everybody learns to appreciate it at some point in their carreer at the institute. So why not learn it now and save yourself a lot of trouble? If you don t beleive it, just ask a student at one of the last semesters... 2 Start Emacs The first thing to do (of course) is to fire up the program. To do so, type at your UNIX prompt: alfred@lada> emacs & 1

2 If everything goes well, you should see a window popping up on your screen presenting you with a welcome message and you re ready to use emacs. If for some reason you would like to open emacs in the terminal window instead of creating its own window, type: alfred@lada> emacs -nw this comes in handy when you re using a ssh connection without graphical capabilities. Last but not least, if you must use those mouse clicks, emacs can probably be started from the menu of whatever window manager you use. 3 Edit Files Buffers Before starting, it is neccesary to mention that Emacs operates with so-called buffers. This simply means that every file you open becomes a buffer which you can edit. Buffers can also contain lots of other stuff like output from an external program, but for now we will consider a buffer as being a file you have opened. Opening a file The first thing to do with your newly started emacs is of course to load a text file into a buffer. In order to do this, a little shortcut terminology is neccesary. The Control key: Nothing unusual here. On the left part of your keyboard you will find the Control key. Whenever you need to use the control key in a shortcut, it will be denoted as: C-<some key>.. which means that you press the control key and the other key simultaneously. To open a file you must press: C-x C-f This will bring up a Find file dialog in the bottom at the Emacs window where you can type the path and name of your text file. Lets say that you want to open the file myfile.txt in your homedirectory. You can choose to type in manually: Find file: /myfile.txt and hit enter. But why not make it easy on yourself? Try typing only my and hit the TAB key. Assuming you have only one file starting with my, emacs will complete the filename for you. If you have more than one file starting with my, a window showing the possible files will pop up. Now you can either supply more letters and hit TAB again or you can click the file you want with the mouse and hit enter. Basic editing Having opened your file, you can move around with the cursor keys and insert text as usual. To copy a line of text, the following procedure can be used: Move the cursor to the beginning of the line. Hit C-k, C-y, move the cursor to a new position and hit C-y. Of course you can also use the normal way of copy/paste in UNIX. Select some text with the mouse, place the cursor elsewhere and hit the middle mouse button. 2

3 Writing/saving a file Having edited you file, you may want to save the results. Do this by pressing C-x C-s. If you want to write it to another filename, use C-x C-w instead and supply the filename in the dialog: Write file: /myfile2.txt Kill your file Finished editing your file? Get rid of it by typing: C-x k (dont press down the control key when typing the k ). The Undo shortcut Eventually you will type something wrong within your emacs or accidentally start a function that you don t want to. The easy way out of whatever you got into is C-g ( gundo?). Try activating the Save as with C-w and abort it with C-g. Exiting emacs At some point you re finished editing and you need to exit emacs. This is done by pressing C-x C-c. If all your buffers are saved, emacs will exit at once. However - if you have unsaved work, you will be prompted whether you want to save it first... More shortcuts The Meta key: Another key widely used in emacs is the Meta key. Depending on which terminal you use, this key is mapped differently. If you use a PC keyboard (which is probably the case), the Meta key is mapped to either your left ALT key or to your left Windows key. Whenever you have to use the Meta key, it is shown as: M-<some key> The following will plot a mandelbrot fractal for you (useful?): M-x mandelbrot..this means that after pressing Meta and x simultaneously you should type mandelbrot and hit return. Here you can also use the TAB key if you re too lazy to type in the full command. Listing all the Emacs commands here would be a waste of bytes and time - instead take a look at the Emacs reference card found on Play around with the commands and get familiar with the basic Emacs functions before proceeding to the next section - here you will need your basic editing skills. 4 Configure Emacs The FSF GNU Emacs can be configured in a myriad of ways and this small section will only give you hints on how to do basic configuration. Emacs will be configured in the language Lisp in the variant Emacs Lisp. In many situations you will often have to just set variables and you do not have to know any Lisp programming to do so. Configuration of Emacs is a very convinient way of making everyday work much easier. Configure Emacs with /.emacs GNU Emacs will read the file /.emacs ($HOME/.emacs) and use the contents to configure how Emacs will behave when you use it. A raw (unconfigured) Emacs will probably, after some use, not behave like you want it to do. Open the.emacs file and write configuration details into the file. The next time you start Emacs the new configuration will take effect. 3

4 emacs & Once in Emacs open the.emacs file with C-x C-f and enter filename /.emacs and press return. (standard-display-european t) ; show european characters (setq user-full-name "Alfred Alfredsen") ; set user fullname (message "Hello, \%s." (user-full-name)) ; say hello to user Instead of restarting Emacs you can execute the following function M-x eval-buffer. Configure Emacs with /.emacs and $HOME/etc/emacs/init.el Soon you.emacs configuration file will be a messy place and all cluttered up. A very efficient scheme for undoing the mess is to use.emacs only for loading the real configuration file. Put the following in your.emacs file ;; load main personal Emacs initialization file (setq load-path (cons (expand-file-name "~/etc/emacs") load-path)) (defvar emacs-startup-file (expand-file-name "~/etc/emacs/init")) ;; recompile initialization file if nescesary ;; Recompile "emacs.el" if nessasary (let ((file (concat emacs-startup-file ".el")) (filec (concat emacs-startup-file ".elc"))) (if (file-newer-than-file-p file filec) (byte-compile-file file))) ;; Now, load everything it! (load emacs-startup-file nil t) You should now put everything configuration detail and initialization into /etc/emacs/init.el. You can use the directory /etc/emacs for further configuration files or for Emacs Lisp packages that you download for the extension of the basic GNU Emacs. Existing Emacs Extensions The existing extensions can be found in the site-lisp area alfred@lada> ls /afs/ies.auc.dk/sw/pack/emacs-20.7/share/emacs/site-l Always substitute the directory emacs-20.7 with the most current version of Emacs. Find the most current version of emacs with alfred@lada> emacs --version GNU Emacs 20.7 Copyright (C) 1999 Free Software Foundation, Inc. GNU Emacs comes with ABSOLUTELY NO WARRANTY. You may redistribute copies of Emacs under the terms of the GNU General Public License. For more information about these matters, see the file named COPYING. 4

5 Setup Colors for Source Code and Texts One example where configuration of GNU Emacs will provide nice results for you to see is with coloring of fonts (global-font-lock-mode t) (setq fock-lock-maximum-decoration t) These two lines will enable almost any editing mode with colors. To setup different colors than the default the following lisp lines will work (setq font-lock-face-attributes ((font-lock-comment-face "Blue") (font-lock-string-face "Red") (font-lock-doc-string-face "Black") (font-lock-keyword-face "SteelBlue") (font-lock-function-name-face "Black") (font-lock-variable-name-face "Black") (font-lock-type-face "Purple") (font-lock-reference-face "Black") (font-lock-string-face "red3"))) New Keyboard Shortcuts Many people at first find Emacs shortcuts strange so why not enstrange people even more by defining your own shortcuts. You should use Control with C (C-c) as it is reserved for user definition of commands. The following lines will define a prefix, a keymap and set a global key for accessing the keymap. (defun Ctl-C-prefix ()) (setq Ctl-C-keymap (make-keymap)) (global-set-key "\C-c" (Ctl-C-prefix)) The only task left is to define which C-c key should do what. Here are a few examples of what you can do (define-key Ctl-C-keymap "c" compile) (define-key Ctl-C-keymap "e" eval-buffer) (define-key Ctl-C-keymap "n" next-error) (define-key Ctl-C-keymap "f" auto-fill-mode) (define-key Ctl-C-keymap "g" goto-line) (define-key Ctl-C-keymap "$" ispell-buffer) (define-key Ctl-C-keymap "-" dabbrev-expand) Further Emacs Configuration For more advanced setup an example is provided at Emacs Course Materials You should also browse the Emacs and related software packages for documentation and information. Use C-h i to reach the GNU information system and choose Emacs to view the documentation. 5

6 5 Edit Latex Files latex-mode When editing L A TEXfiles it is nice to have correct coloring of the L A TEXcommands etc. When you start an Emacs on the UNIX system you should automaticly be set. If this does not happen you should add the following to your.emacs: (require tex-site tex-site ) This will use AUC-TeX as the default mode for editing LaTeX files. For more information on AUC-TeX see the next section. You can see that you are using the LaTeX in Emacs since the should be a LaTeX in your Emacs status bar. AUC-TeX First of all. AUC-TeX can be found on SunSITE.dk. AUC-TeX gives you a lot of advantages through keyboard short-cuts and through the menues. AUC-TeX used together with Ref-TeX makes a strong pair for writing reports. For information about Ref-TeX see the Ref-TeX section. Basicly the advantages of AUC-TeX is in when inserting environments, changing fonts and building a part of the document or the whole document. For a more in-depth information on AUC-TeX consult the info-pages on AUC-Tex. In this guide the focus will be on the keyboard short-cuts since you can easily enough navigate in the menues. For instance to change to a bold font you type nearly nothing. By pressing : C-c C-f C-b textbf however AUC-TeX gives you that for AUC-TeX will insert the textbf. To see how which fonts AUC-TeX will insert you can press: C-c C-f h As mentioned above to AUC-TeX can also be used to insert L A TEX environments. To insert an environment use the short-cut: C-c C-e Use the tab-key to see which enviroments you can insert. AUC-TeX can also insert section command. To insert a section or chapter press: C-c C-s Finally you can build and view you document from Emacs. AUC-TeX has both support for compiling your master file (see the next section for more information) and the buffer you are currently working in. To compile the document you press : C-c C-c this will build the master file. To just compile the buffer press : C-c C-b. To compile you document you need to have setup the master file. Master File In AUC-TeX the master file refers to the file that contains the whole document. This means that if you are writing a large document like a technical report the master file is the file where all the sections and chapter are put together. In the case of a small document the master file is just the file it self. Basicly you can set the master file in two different ways. You can either set it staticly or you can make AUC-TeX ask you what the master file is. To set a static master file insert this in your.emacs file: (setq TeX-master /path/to/master/file ) 6

7 To have AUC-TeX ask you insert: (setq TeX-master nil) This will insert the following in the bottom of your tex file: %%% Local Variables: %%% mode: latex %%% TeX-master: t %%% End: If TeX-master: is t it means the file is a master file. Other wise it is a path to the master file. To use AUC-TeX to build you document insert the following in your emacs start-up file to have some reasonable values: (setq TeX-region (concat (user-login-name) "-region")) (setq TeX-command-default "latex") RefTeX-mode Ref-TeX hooks in nicely with AUC-TeX and also uses the master file. You can use Ref-TeX when you are inserting reference to sections, figure, and litterature. You can also use Ref-TeX to insert unique labels and navigate your document. Ref-TeX is quite interactive and you can normally get some help pressing the?-key. To use Ref-TeX insert the following in your emacs startup file: (add-hook LaTeX-mode-hook (lambda () (reftex-mode t))) (setq reftex-plug-into-auctex t) The most common functions is: inserting reference to figures or section, Inserting bibliography reference, following a cross-reference, and seeing a table of content. To make a label - type: C-c (. To insert af reference to a label type: C-c ). To insert a cite to a piece of litterature type: C-c [. To jump to a label when you are standing on it type: C-c &. And to build a table of content of your document type: C-c = 6 Edit Source Code: Java, Matlab, C Emacs is the one most used tool for writing source code. There are many tools in GNU Emacs that will help you to write source code better and unfortunately not all programmers use these tools. Here is an overview of the most important ones. To summarize the conclusion first you will have to use emacs tags (etags), dynamic (and hippie) abbreviation expansion to instantly expand on variables and more, font lock mode to edit source code with colors, use GUD mode (gnu universal debugger) to debug your programs, use the modifiable compile command, etc. Some of these issues are explained below. 7

8 Change Editing Mode for Source Code Normally GNU Emacs will change the editing mode based on the suffix of the current file you are editing. To add additional modes please configure GNU Emacs with the automode feature (setq auto-mode-alist (append (("\\.cps$". postscript-mode) ("\\.ps$". postscript-mode) ("\\.py$". python-mode) ("\\.po[tx]?\\ \\ \\.po\\.". po-mode) ("\\.s?html?\\ ". html-helper-mode) ) auto-mode-alist)) If you even stranger editing modes than this then change the major editing mode by hand with M-x c-mode or any other mode you need for editing the source code. Dynamic Abbreviation Expansion: M-/ When you program you should develop a habit of loading most of your files with source code into buffers of Emacs. Configure your personal Emacs settings with this (require iswitchb) (iswitchb-default-keybindings) (require uniquify) (setq uniquify-buffer-name-style forward) (load-library "yic-buffer") Now you can change between buffers more easily and now use C-x b to change buffers in the follwing way: When pressing C-x b to change buffers then you can use C-s to scroll forward in buffers and C-r to scroll backwards. Also you can type in part of the buffer name to reduce the search possibilities. As an example you can type in scr to get to the *scratch* buffer. The lisp package uniquify see to that if you have several files opened in different buffers then they have unique names based on directory names instead of the <1>, <2>, and so forth numbering scheme. Also develop the habit of using manual pages and show them within Emacs by using M-x man and enter the manual page you want to view. Keep these manual pages in buffers, you will need them afterwards when making dynamic abbreviation expansion. Dynamic abbreviation expansion: Use the M-/ to complete a word based on open buffers in Emacs. This is one of Emacs most advanced and useful features which can be used in any buffer in any mode. When editing source code you can use M-/ to expand either function names or variable names based on the content of all open buffers. Therefore it is useful to keep all files of your coding project along with manual pages open while editing! The important of dynamic abbreviation expansion cannot be overstated! Font Lock Mode For every buffer you edit most often you can color the contents based on the syntax. You have to issue a M-x font-lock-mode to turn coloring on or off. Please see section 4 for more information on configuring font coloring based on syntax in GNU Emacs. 8

9 Compile Command One useful feature of GNU Emacs is that it can automatically invoke the gmake or make program in the directory you work in. An example of configuring the compile command is (setq compilation-window-height 2) (setq compile-command "gmake -k") (setq compilation-scroll-output nil) You can then add a keyboard shortcut like this or (define-key Ctl-C-keymap "0" compile) (define-key Ctl-C-keymap "c" compile) Please see section 4 for more information on configuring your keyboard setup. 9