Tutorial, Part I

C211 and H211, Fall 1996



We shall be using the computers named copper and zinc, which run the UNIX operating system. Use your network ID (your username) to create accounts on copper and on zinc following directions provided by UCS. You can connect to copper or zinc from any microcomputer cluster, or from a home computer via a modem.

This tutorial provides a basic introduction to the software tools we suggest you use in this course. Read this material through first and then try out the instructions on the computer. Refer back to this material when necessary throughout the course. If you need help, ask a consultant or any of your instructors to show you how. Experiment with the computer outside the requirements of the course. It's fun and will make you more comfortable with the software required by the course.

UCS provides many handouts to help you learn about the computing environment at IU, and they ofer classes to help you get started with computers. Below is a list of pamphlets you might want to look at.

This list is by no means complete; so look over other UCS handouts as well, or check out this link.

Getting Started

Logging In

You can log in to copper or zinc from any machine in any UCS cluster, or any other machine on IUBnet (the Bloomington campus network), including telephone modem access. Since PCs and Macs are the most common, this tutorial will give instructions using these microcomputers. For help logging in from somewhere else, talk to a UCS consultant or one of your instructors.

In this tutorial we explain what we believe to be the simplest and generally most satisfactory ways of accomplishing things, but there are usually other ways to do the same thing. For example, on UCS PCs telnet can be accessed from Windows as well as the menu access we describe below. In Windows the telnet font is smaller, but it is possible to switch to other Windows applications, such as Netscape, without leaving your telnet session.

You are encouraged to explore the wondrous complexities of our software environment, and in the process you will doubtless discover other approaches that you prefer at least some of the time. As in all things, this exploration should be pursued in moderation--don't neglect other aspects of life!

From a PC

In the Program Manager folder, double-click the mouse on the icon labelled LAN WorkPlace Telnet & FTP. To login to copper, double-click the icon labelled copper. To login to zinc, double-click the icon labelled zinc, if it exits. If there is no such icon, then double-click on Enter Your Own Node and then type zinc in the Hostname field of the dialog box that appears.

Skip the following Macintosh information for further instructions.

From a Macintosh

Double-click the mouse on the filing cabinet named MACINTOSH in the upper right of the screen (unless this window is already open). You will see a window containing many folders with names under them. Double-click the mouse on the folder called Communications.

Now you will see a collection of icons, with one named copper and one named zinc; double-click the appropriate one. If the zinc icon is not present, you can still login to zinc by selecting some other icon, say the copper icon. Then select Open Connection from the File menu, and enter zinc in the Host/Session Name field of the dialog box that appears. In any case, the Telnet program will start up in a new window with the login prompt.

After starting Telnet

The login prompt asks for your username. After entering your username, hit the Return or Enter key, hereafter indicated by <CR>. You are next prompted for your password. Your password will not show up as you enter it. After entering your password, you must also enter <CR>. Since you must almost always press <CR> after entering something, we won't mention <CR> again.

If you receive an Incorrect Password error, try typing your username and password again, slowly and carefully. If repeated attempts fail, see a consultant.

Once you've successfully entered your username and password, the computer prints out a welcoming message. If this is the first time you are using this account, then you will be prompted for a shell. We recommend that you select tcsh as your shell. (The chsh command can be used later, at any time, to change your shell, if you've already selected something else.) You should now see the UNIX shell prompt, which is either copper ~> or zinc ~>. (The ~ indicates you are in your home directory. The prompt will be modified accordingly if you move to another directory.) At this prompt you may enter any UNIX command.

Logging Out

It is very important that you log out of your account when you are done using the computer, or if you leave the computer unattended. Failure to do so allows others to look at and and possibly damage your private files, to misrepresent you to others (by sending e-mail from your account), and to gain access to other computer systems on which you have accounts. To log out, enter the UNIX command logout.

On the PC you will be returned to the Communications menu, on the Macintosh you will be left in the Telnet program and then need to select Quit from the File menu to exit the telnet program.

Getting Help

We will be using a number of UNIX programs, and you may have questions about some of these that we have not anticipated. A useful tool for getting help is the man (short for manual) command. For example, to see documentation on the ls command, enter the command man ls. The emacs editor has its own built-in tutorial and help system, which we describe below. You may want to go through some of the on-line tutorial that is built into emacs to get a broader picture of what it can do. Emacs is an extraordinarily powerful editor; we only touch on its capabilities in this tutorial.

Brief Overview of UNIX Commands

The UNIX commands introduced here will help you to look at what you've done, to change it, and to delete it. You may want to look at a copy of UCS's UNIX guide which provides a more extensive introduction to the vast array of UNIX commands. Read this section through, then finish the tutorial and come back. By then you will have created some files that you can manipulate with the following commands.

UNIX commands may only be entered at the shell prompt. If a typing mistake is made, it can be erased with the Delete key. Each time you press the Delete key, the cursor moves one space to the left, erasing the character in that space.

Listing Files

You start out in your home directory. To see what files are in the current directory, use the ls command. Try it and you will see something like:

copper ~> ls

Your home directory comes with an empty bin directory, that you will have no need for in this course. For now just keep it simple by staying in your home directory. After you've finished the tutorial below, try this command again. By then you will have created more files in your home directory.

There are a few more files in your account. These are "dot" files which contain information to configure your account. To see these files, you type

copper ~> ls -a

You will see a number of files such as .login and .profile. Do not delete any of these "dot" files.

Copying Files

Now to copy the file .login to a file named test1.txt, type the following at the prompt:

cp .login test1.txt

You can name the copy anything you want, as long a name as you want. (Any letter or number may be used in a UNIX name, as well as some special characters such as dot.) UNIX, unlike some other operating systems such as DOS, is case sensitive: upper and lower case versions of the same letter are considered to be different. You should try to keep the extension after the dot the same, since that tells you what kind of file it is. Scheme files generally end in .ss and text files often end in .txt. You can see if the copy was made by entering the command ls. cp does not remove the original file.

To try this on your own, copy the file test1, which you just created, into a file test2.txt. When you type ls, you should see three file names: bin, test1.txt, and test2.txt.

Moving Files

Use the command mv move a file from one directory to another, or just change the name of a file.

mv test2.txt test3.txt

Now there should be no file test2.txt, and a new file test3.txt that is exactly what test2.txt was.

Deleting Files

Delete files with the command rm, short for "remove":

rm test3.txt

This deletes the file test3.txt from your directory. Be very careful when using this command; you may not be able to get the file back if you delete it accidentally.

Viewing Files

To look at what is in the file test1.txt, you can type

more test1.txt


cat test1.txt

The first shows you the contents of the file, one screenful at a time. Press the space bar to go from screen to screen. Hit return to move down one line at a time. Type q to quit (get back to the shell prompt) before the end of the file. cat scrolls through the whole file without stopping.

Printing Files

Many clusters have line printers that are accessible from the machine you are connected to. The name of the line printer is usually indicated on a label taped to it. If you must use a laser printer, you can access the printer in LH004 by the name cs_ps10. You should only print to that printer when you are in one of the microcomputer clusters in Lindley Hall (the machines in LH004 itself require a different computer account). You may also "download" the file you want to print onto the microcomputer you are using and then print it out on the cluster laser printer. Ask a consultant for help if you don't know how to print from a particular cluster. If you are printing directly from copper, use the following commands:

To print a file to a given printer, say cs_ps10, use the lpr command with the argument -Pcs_ps10. For example, to print text1.txt to the laser printer in LH004, type:

lpr -Pcs_ps10 save.txt

Sometimes many people print files at the same time. You can look at the list of files waiting to be printed using the command:

lpq -Pprinter-name

If you are picking up your printout immediately and the printer is not busy, you use the -h flag, which tells the printer not to print a header page with your name on it:

lpr -Pprinter-name -h filename

If you change your mind about printing a file, and it has not started to print, you can use the command lprm to remove it from the queue of files. You will need to specify the job number of the print job you wish to kill. You can get this number from the listing produced by the lpq command. Use man lprm to find out more about it.

Using Scheme

To start Scheme from the shell, just use the command scheme (If you have much to do in Scheme, run it in emacs instead. We'll get to that presently.) Scheme greets you with a message identifying itself and then the Chez Scheme prompt >. At the Scheme prompt you can enter any Scheme expression. For example
copper ~> scheme
Chez Scheme Version 4.1b
Copyright (c) 1991 Cadence Research Systems
> (+ 3 4)

When you press <CR>, Chez Scheme's read-eval-print loop evaluates the expression and prints the answer 7. Then you again get the prompt >. Enter 'cat, making sure you type the apostrophe before the word cat. Chez Scheme returns cat and then prompts with >. Chez Scheme is case insensitive. Regardless of whether quoted variables are entered in upper- or lower-case letters, Chez Scheme returns them in lower-case letters. Now enter 15 and we see that 15 is returned. Numbers need not be quoted when they are entered; they are self-evaluating. The symbol cat is not self-evaluating: we had to quote cat in order to have it interpreted literally as the symbol cat. Now enter cat without the quote. You get a message which tells you that the variable cat is not bound (don't worry about the "debugger" information for now, every error causes that to appear). cat, unquoted, is a variable that has not yet been given a value.

Now observe the results of entering each of the following expressions in response to the Scheme prompt. Can you explain the results in each case?

(cat dog mouse)
'(cat dog mouse)
(+ 1 2 3 4 5)
'(+ 1 2 3 4 5)
'(car '(one two three))
(car '(one two three))
(cdr '(one two three))
(cons 'one '(two three))

We exit from Scheme and return to the shell prompt by responding to the Scheme prompt with

> (exit)

or by typing C-d. (This is our notation for control-d; hold down the control, or ctrl, key while pressing the d key.)

The Emacs Editor

In the above exercises, you entered the expressions while Scheme was invoked from the UNIX shell. Once you entered an expression and it was evaluated, there was no way to get it back to change it, or to save it to a file for later work. It is usually more convenient to enter expressions in an editor and then transfer them to Scheme for evaluation. This allows you to keep a permanent record of what you write by storing the expressions in a file in your account. We will be using the emacs editor. It is very powerful for program development and many other uses, it is widely available, and it allows Scheme to be run within the editor. To see how this is done, enter the command emacs at the shell prompt. For example

emacs test.ss

Giving emacs a filename argument, such as test.ss, causes emacs to load the given file for editing if it exists, or start a new buffer for creating the file if it does not exist.

You will now see a blank window with the cursor at the upper left corner and a banner at the bottom displaying Emacs and some other information such as (Scheme), indicating that the editor is in its Scheme mode.

Now type

(car '(one two three))

again and observe that when you close each pair of parentheses, the cursor bounces to show you the matching opening parentheses. The expression is not being entered in Scheme itself, so you will not see the result of its evaluation, but it can be sent to Scheme at any time, as we shall see. Press DEL (the delete key) and notice what happens: it erases the character to the left of the cursor.

We shall next learn to use the editing commands of Emacs. In Scheme mode emacs bounces the cursor for parenthesis matching and some other tricks that are great for Scheme programming, but not when you are typing prose (say in English). For that you want to be in text mode. We switch from the Scheme mode to text mode by pressing ESC (the escape key), releasing it, then pressing x. Note that M-x appears at the left end of the banner at the bottom of the screen. Now type text-mode<CR>. In the future, typing such a sequence will be indicated by M-x text-mode. (M-x is read "meta x". On some keyboards M-x may also be entered by holding down a meta or alt key while pressing x.)

Notice that now the word (Text) appears in the banner at the bottom of the screen. When you call up Emacs with a filename ending with the extension .txt, Emacs goes directly into Text mode, whereas when the filename has the extension .ss, it automatically goes into Scheme mode.

When entering emacs command names after the M-x (read "meta x") prompt, you can hit the space bar to cause Emacs to show you all the current completions of the command you are entering. This can save you from typing the whole command.

Getting Help

The command C-h (control-h) invokes the emacs help facility. Type C-h again for a brief list of help options, or a third time for a full page description of help options. As always when emacs is prompting for more input at the bottom of the screen you can abort the command that is prompting for information by typing C-g.

Moving Around

Now type a few lines of text. To move the cursor up, press C-p, (p for "previous"). Repeat this until the cursor is on the first line of your text. Press C-n to move the cursor down again (n for "next"). Move the cursor up again to the first line of your text. If it is not at the beginning of the line, press C-a. Now press C-f and note that the cursor moves "forward" one space. Next press C-b, the cursor moves "back" one space.

To move forward over one word, use the command M-f. (Recall this is read "meta f" and may be entered by pressing ESC and then f.) Next try M-b and watch the cursor move backward one word. You can abort a command or sequence of keystrokes with C-g. For example if you have typed ESC, but then decide that you want to move forward a character, enter C-g to abort the ESC keystroke, and then enter C-f. Try it.

Now enter C-e. The cursor moves to the right end of the current line. Entering C-a moves it back to the beginning of the current line. Two additional commands that you will find useful are C-v which moves ahead to the next screen and M-v, which moves back to the previous screen.

Deleting Text

We saw that DEL deleted the character to the left of the cursor. Now press C-d and note that the character directly under the cursor is deleted. Retype the letter that was deleted. Now press C-k. This deletes (kills) whatever is to the right of the cursor on that line and stores it in a "kill buffer". If you press C-y, the last thing stored in the kill buffer is copied into the position starting at the cursor. Try it.

Saving a File

Observe that there are two asterisks (stars) at the left end of the banner. These indicate that the buffer you have been working in has new material that has not been saved to a file. To save what you have done in a file called mytext.txt, enter C-x C-w (control-x followed by control-w, the "w" stands for "write file"). You will see a prompt in a mini-buffer at the bottom left of the screen under the banner asking for the name of the file. Type mytext.txt and wait until a message is displayed in the mini-buffer indicating that the file has been written. After it has been written, the two asterisks disappear. Note that the filename with its extension appears in the banner line just after the word Emacs:. If you want to save the buffer to the same filename, you can enter C-x C-w and then <CR> instead of typing a filename. If you are using a PC and not a Mac, you can also save a buffer to a file using C-x C-s, which saves the buffer to the current filename. On the Mac, C-s causes the whole Telnet window to pause, and you must hit C-q to get it going again.

Inserting a File

The command C-x i is used to insert the contents of a file at the current buffer position. It prompts for the name of the file to insert using the mini-buffer, in the same manner as the C-x C-w command. Trying this now using the file you just saved will give you two copies of your material in the buffer.

Undoing Mistakes

If you make a mistake, such as accidentally deleting text, you can undo it with the command C-x u. This is particularly handy if you accidentally type a control-key combination that you have not learned and it does something completely unexpected!

Running Scheme in Emacs

You can run Scheme within Emacs directly with the command M-x run-scheme. This creates a buffer in which Scheme runs directly, and you can use Scheme just as you would outside of Emacs.

Sending Mail

To send mail from within emacs, enter C-x m. A new buffer will appear with the cursor after To:. Enter the email address that is to receive your mail on this line (or multiple addresses separated by commas). Enter a brief description of your message following Subject: on the next line. Then move the cursor to the end of the buffer and compose your message. When you are ready to send the message, enter C-c C-c. It will be sent and the buffer will disappear. We will discuss receiving mail in Part 2. We shall also describe the use of the Elm mailer which you may find simpler to use.

Exiting Emacs

To quit Emacs, enter C-x C-c. If there are unsaved files or sub-processes (like Scheme) running you will be prompted to decide what to do with them. Be careful to save any work you want to keep.

Below is a summary of the Emacs commands used in this tutorial. You will have a chance to use them in the assignment which follows the summary.

Summary of Selected Emacs Commands

Keystrokes Effect
C-f Move cursor Forward one character. May use right arrow key.
C-b Move cursor Backward one character. May use left arrow key.
C-n Move cursor down to Next line. May use down arrow key.
C-p Move cursor up to Previous line. May use up arrow key.
C-e Move cursor to End of line.
C-a Move cursor to beginning of line.
C-h Enter the Emacs help facility.
DEL Delete the character before the cursor.
C-d Delete the character at the cursor.
C-k Kill the rest of the line from the cursor to the end of the line.
C-y Unkill (yank back to current cursor position) the last thing killed.
C-v Display the next screen.
M-v Display the previous screen.
C-x C-v Load a new file into the current buffer. Prompts for a file name.
C-x C-w Write the whole buffer to a file. Prompts for a file name.
C-x i Insert file. Prompts for the file name.
C-x u Undo the last text modification.
M-x run-scheme Run Scheme in its own emacs window.
M-x text-mode Enter text mode.
M-x scheme-mode Enter Scheme mode.
M-x shell Start a UNIX shell in an emacs window.
C-x m Send an email message.
C-x C-c Exits from Emacs.

As time goes on, you will probably want to become familiar with more Emacs commands to speed up your work and allow you to do more things. There is a more complete GNU Emacs Reference Card available from UCS.

Tutorial, Part II