CPS 100, Fall 2000, Unix/Emacs Intro

• Copying, moving, deleting files
• Traversing and moving between directories
• Invoking programs including editors and compilers
• Edit, compile, debug, and run a C++ program

This section comes in several parts. You will login, reconfigure certain files to facilitate using libraries in conjunction with this course, practice some UNIX commands, and write a simple C++ program. This document is only a brief introduction to many tools. You will need to spend some time on your own experimenting further to become comfortable with the tools. You should consult the OIT online help page for more information.

In this document, commands that you type will be in a font that looks like this, sometimes commands may be quoted --- "like this" --- do not type the quotes, just type what is between them. When instructed to type something, press the return key after typing it.

Logging in

1. Workstations are always on, do NOT turn them off. Wiggle the mouse if the screen is blank.

2. If you're using a PC in a cluster you will first need to start X windows by either clicking on the X icon, OR clicking on Start at the bottom left corner, then clicking on Programs, and then clicking on X-Win32.

   You should see a line at the bottom of your screen that says "X Win32". Not much else happens yet.

3. From a PC you need to open a connection to a unix machine. We will be using "ssh telnet", also called TeraTerm Pro. Click on the ssh icon, OR click on Start at the bottom left corner, then click on Programs, and then click on "Tera Term Pro".

   You will see one of the following machines to login to (or if none appears, enter one of these)

       godzilla.acpub.duke.edu
       kiosk.acpub.duke.edu
   

   (Hint: Use tabs to move between fields). Type your duke login-id, then a tab, then type your password (your password is not displayed).

Note: passwords are case sensitive, Banana is different from banana.

4. A unix xterm window should be displayed and a message indicated that you have successfully logged on.

Getting Started with UNIX

To enter a command, type after the prompt in one of the xterm windows. You should see a prompt that may look similar to

    [1] rodger@godzilla2%

If this is a new account, you should change your password to something that is easier to remember, but not easy for someone to guess. Do not use your name, or an English word, but rather compose a password formed with numbers, upper and lower case letters, and punctuation marks. To change your password, type the UNIX command  passwd and follow the directions it prints.

Next, from in the xterm window, at the prompt type ~ola/bin/setup cps100. This runs a program that will set up some files in your directory to make it easier to use the programming tools we provide---it does this by copying some dot files (like .cshrc, see below from  ~ola/newuser). Additionally, it creates a cps100 directory in your account (if you don't already have one) and sets the permissions properly as called for in assignment zero.

Any files changed by this program are saved with a .old  extension, e.g., .cshrc.old.  If you do not get a prompt back after typing the command, consult a TA.  If you do not want to run this program because you have made your own changes to your accounts setup, you will need to look at the setup program to determine which parts of it you want to setup. Some are needed for accessing and submitting files. PLEASE CONSULT A TA if you are not sure.

In order for changes made by the setup command to take effect, you will need to logout from the unix window and then log back in. To logout of your unix window, type logout . Now, please log out, then log back in.

Creating and Traversing Directories

When you login, your session begins in your main directory. To see the name of your directory, type the UNIX command pwd (print working directory).  The complete name it prints in your terminal window should look similar to /afs/acpub.duke.edu/users/r/o/rodger except your login-id should be the rightmost word.

1. To list your files and directories, type ls (think of this as shorthand "list"). You should see the directory you just created listed.
2. You can cd (change directory) into your cps100 subdirectory by typing cd cps100. Typing pwd should show you in the directory you just changed into. You might now make, for example, a directory called yahtzee by typing mkdir yahtzee. Then change into this by typing cd yahtzee.

At any time, you can type cd (with no arguments) to return to your home directory. Instructions for editing, compiling, and printing are given below. To work on an assignment you'll normally copy one or more files into a directory in which you'll do work for the assignment. The copy command is cp so from within your yahtzee directory (for example) type (do not forget the trailing dot: "."):

Type ls to see that the files were copied. You should see a new file called Makefile. We will use the Makefile to compile programs in this course.  This Makefile will automatically link to libraries that will be used in this course. You can use it without modification for any C++ program you write as long as the complete program is in one file. If you write a program in multiple files, you will need to modify the Makefile slightly to tell it which files to combine together to make your program.

Test Program: Edit, Compile, Debug

Starting the editor xemacs

 xemacs  & 

An xemacs window should appear (please be patient!). You can use the arrow keys and the mouse to move around in the xemacs window.

Loading, Editing, Saving Files

• Use the file menu to load a file (even one that does not exist yet). Click and hold the menu and choose Open File before releasing the mouse button.
(alternatively, you can use cntrl-x cntrl-f, that is hold down the control key and press x followed by f as a substitute for using the menu.)
• The prompt for Find file: appears in the small minibuffer window at the bottom of the xemacs window. You should also see a path which might be ~/ or ~/groupcps6/aug29/. If you do not see this, consult with a TA because you may not be in the correct directory. You can edit what appears in the minibuffer with arrow/delete keys.
• You will create a file named lorax.cpp. To do so complete the path in the minibuffer so that it reads ~/groupcps6/aug29/lorax.cpp and press return.
• Enter the C++ program shown previously. Be careful that you type it just as it appears. You will notice sometimes after you type something, the cursor will "automagically" move to another position to indent properly. When you type a "}", the cursor always jumps back to the "{" for a second so you can see if the "}" matches with the correct "{".  These are features of the xemacs editor meant to make it easier for you to complete your programs.
• If you make a mistake, use the arrow keys or mouse to move around and edit in the window.  You can use the mouse to position the cursor within xemacs by clicking in the window where you want to type.  You can also use the arrow keys and the scroll bar to move around.

In general, you should always have an xemacs window open. Unless you are logging off, there is seldom a reason to quit xemacs. You can, however iconify (make small) the window by clicking the mouse on the dot-button in the upper right of the window. This works for any window. Double-clicking on an icon opens that application.

Until you save your file, it is stored in a temporary buffer (the region in xemacs in which you are typing). When you believe the C++ program is correct, save it by clicking the File button at the top of the xemacs window, and then selecting Save Buffer. A message that the buffer has been written should appear in the minibuffer.  You should save your program often to ensure none of your changes are lost inadvertently.  You will not be granted any leniency if you lose your work because you did not save it properly. You can type cntrl-x cntrl-s to save instead of using the mouse.

Compiling a C++ program

1. Use the Compile option under the Tools menu.
2. The command make -k, which appears in the minibuffer, is the default compile command. You should compile by editing this command so that it reads make -k lorax, then hit return. It may take a while for the program to compile, but you should see an xemacs sub-window with an indication that something is happening.
3. If there is a syntax error in the program, a message will appear in the *compilation* buffer. To get to the error you can click on the error with the middle mouse button. This will take your cursor to the line on which the error appears, so you can use it to cycle through multiple errors, fix them, and then recompile.

If there are multiple error messages, fix the first one only and then recompile. Sometimes one error causes the compiler to list additional errors that are not really errors.

An example of an error message is:

lorax.cpp:5: unterminated string or character constant lorax.cpp:5: possible real start of unterminated constant

This message tells you the name of the file (lorax.cpp), the line number the error occurred near (line 5) and a guess as to what is wrong. You do not need to worry about where line 5 is since clicking on the error message takes you there.

If you do not have any errors with the first compile, you might want to modify the program so that there is an error. For example, remove a semi-colon and then compile the program.

Execute your program

• In an xterm window, type ls to see the files in you aug29 directory.

You should see both lorax.cpp and lorax. The file lorax is an executable program. You might also see a file called lorax.cpp~. This is a backup copy of your program that xemacs automatically creates. It is not an exact copy, but rather a copy before you made your most recent changes.
• To run any executable program, type its name in your terminal window, so type lorax to execute this program.
• You can type ls -l  to see how big the files are and when they were created.