Comprehensive System Administration
Lecture 3 notes:
New students?
If you are new this week, you need to check with the instructors to see if there is any room. The class may be full.administrivia:
Enrollment Any problems? Please email me to get on the course announcement list: jones@csua.berkeley.edu Homework? Feedback? Troubles? Getting Help If you have trouble, please email me, or one of the other teachers. The OCF staffers are often around the lab, and can be helpful. Don't forget your classmates. Questions?course material:
Last week we covered basic unix commands. This week we'll be looking at text editors, focusing on the "vi" editor. We'll go over some basic commands, and then turn you loose on tutor.vi to experiment and get familiar with vi. If you are already familiar with the standard editors, help the folks who are new to it! Thanks goes to Shin Ae Tassia for pointing out this useful tutorial. Goals: Using vi: opening and closing files moving around adding text deleting text searching for text replacing text moving text Using Emacs: opening and closing files moving about the file basic editing online helpfiles Using Pico: Using pico is quite easy When not to use picoWhat is a text editor
A program for inserting or appending text to a file. A text editor is not a word processor, although some text editors do include word processing functionality.A History of Unix editors
Vi is the most widely used editor, reliably coming preinstalled on all current unix and unix like OSs. Many people think it's a strange choice because its user interface leaves a lot to be desired. It's the standard because it's a fast editor for expert users, and, circularly, for the reason that it comes preinstalled on all current unix systems, and has for some time. This is not the case for many other popular editors, and there was a time that even vi didn't come installed be default. In those days, one was expected to know a line editor - ed, or ex - in order to edit files, at least until you could get the system on a network and ftp a more friendly editor such as vi. What is a line editor? Editors like vi and emacs are called 'screen editors' because when you edit a file, it fills the screen with the file's text, and lets you edit it and navigate around the file's contents while viewing it on the screen. This is such a good idea that you've never heard "screen editing" called anything before -it's just the way that you would want to edit a file, how else would you do it? Well, before the days of terminals that knew how to move the cursor back up a line on the screen - especially teletype terminals, which were glorified typewriters/daisy-wheel printers that printed all the characters instead of displaying them on a screen - file editors had no choice but to display a file one line at a time, and allow the user to make changes to that line. For instance, when editing a file with ed, first the user would type the line number of the line to edit, then make changes to that line using special commands.Using vi
vi is the "visual" full-screen interface to the ex editor. % vi filename will open or create a file named filename vi has two modes, command mode and text-input mode. To enter text input mode, hit a (append) or i (insert). To get out of text input mode, hit escape. If you are unsure what mode you are in, you can resolve the ambiguity by hitting escape until you are in the command mode. We went over the most basic vi commands in class (from the vi manpage): The commands to move around the file are: h Move the cursor left one character. j Move the cursor down one line. k Move the cursor up one line. l Move the cursor right one character. <cursor-arrows> The cursor arrow keys should work, too. On some terminals, cursor keys send unexpected characters. A common symptom of this is to get a capital A, B, C or D appearing on the line above the cursor when using the cursor-arrows while in text-entry mode. /text<carriage-return> Search for the string ``text'' in the file, and move the cursor to its first character. The commands to enter new text are: a Append new text, after the cursor. i Insert new text, before the cursor. o Open a new line below the line the cursor is on, and start entering text. <escape> Once you've entered input mode using the one of the a, i, O or o commands, useto quit enter- ing text and return to command mode. The commands to copy text are: yy Copy the line the cursor is on. p Append the copied line after the line the cursor is on. The commands to delete text are: dd Delete the line the cursor is on. dw Delete from the cursor to the end of the word the cursor is on. x Delete the character the cursor is on. The commands to write the file are: :w<carriage-return> Write the file back to the file with the name that you originally used as an argument on the vi com- mand line. :w file_name<carriage-return> Write the file back to the file with the name ``file_name''. The commands to quit editing and exit the editor are: :q<carriage-return> Quit editing and leave vi (if you've modified the file, but not saved your changes, vi will refuse to quit). :wq<carriage-return> Save your changes, if any, and quit. :q!<carriage-return> Quit, discarding any modifications that you may have made. One final caution. Unusual characters can take up more than one column on the screen, and long lines can take up more than a single screen line. The above commands work on ``physical'' characters and lines, i.e. they affect the entire line no matter how many screen lines it takes up and the entire character no matter how many screen columns it takes up. After going over these basic commands, we turned the class loose on the vi tutorial, which was assigned as homework. Using Emacs
We didn't get a chance to cover emacs, which is another powerful text editor. It is favored by programmers, and has a richer, more complex and featureful interface. It is very widely used, although it doesn't come standard on every system, Other notes: xemacs vs emacs - two branches of the software being maintained by different parties.Using pico
pico is a very simple text editor, which uses the cursor keys to move around, and lists other basic commands which are available at the bottom of the screen. Pico is sometimes nice for editing html or messages to others (it is nearly the same editor you use as the default editor in the pine email client (pico stands for pine composer)). I like the ^J (control-J), Justify, command, which wraps all the text nicely according to your window. other notes: pico by default wraps lines, which makes it best for writing letters or editing html, or doing anything where you would prefer the lines don't get overly long. To turn off this feature use the -w flag: pico -w filename wrapped lines can be especially dangerous in configuration files such as the passwd file, where the format is expected to be a certain way.Homework #2
To learn more about vi, read the vi manpage, and go over tutor.vi, a vi tutorial, at least until lesson 4. The "ls" command is probably one of your most used commands. Did you ever read its manpage? What to turn in: What letters of the alphabet are not valid ls flags? Describe a problem you have with vi (user interface, etc.). Class Feedback: Do you have any questions about the class? What would you like to learn? Do you feel that the lectures are going too fast/too slow/just right? Attach a copy of your modified tutor.vi, and mail the answers to the above questions to: jones@xcf.berkeley.edu (note that's not jones@ocf, mail to jones@ocf may go unnoticed).
enrichment
Here are some links and information you might find useful or interesting. A quick ed tutorial emacs survival guide (small) vi FAQ from comp.editors newsgroup vi primer Using the vi editor Useful Linux Programs Don't forget to look at the manpages for the commands that you've learned. The manpage for ed is short compared to other editors.