CPS 108: Getting Started

Spring 1999

Due before your next class meeting

This document will show how to:

Login to and logout from the Sun Ultra-SPARCstations found on campus
Use basic UNIX tools, including:

Copying, moving, deleting files
Traversing and moving between directories
Invoking programs including editors and compilers

Edit, compile, debug, and run a C++ program
Use Netscape to access web pages including the page for the course

This lab comes in several parts. You will login, reconfigure certain files to facilitate working in CPS 108, practice some UNIX commands, write a simple C++ program, and use netscape. 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.

If you view this lab using a web browser like Netscape you will be able to jump between sections by clicking on highlighted words, i.e., links. An explanation about how to use netscape is given below. The pieces of this document include:

Logging in

Log in to a workstation. If you have problems logging in ask a TA for help. (You may need to go to the OIT Help desk in 101 North Building, although engineering students may need to check with the engineering school office or the dean's office.) To log in:

Find a free workstation.

NOT

Type your login-id, hit return, type your password (your password is not displayed).

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

Wait until two windows labeled xterm appear, this may happen quickly or take a while.

left

Managing Windows in X

The two rectangles labeled xterm are called windows. The row of small rectangles containing pictures in the top left position of the screen is a menubar which contains some icons. Icons represent windows that are temporarily hidden. Click the mouse (left button) on the picture of the calculator (also labeled xcalc) and wait until a calculator appears on the screen.

The green with black dots covering most of the screen is called the background. Move the mouse to any area of the background and try clicking the three mouse buttons each at a different time. Each button brings up a different menu of applications. Do not try any of these now, you can try them on your own later.
Most windows have title bars across the top of the window. Move the mouse to the title bar for the calculator window. Click and hold the left mouse button on the word Calculator. Move the mouse and the window should follow. Let go and the window will be in its new position. (Note: You can also move windows using the Window Ops commands that appear when you click and hold the left mouse button when the mouse points to the background.)
Another useful window command is resizing the window. Move the mouse cursor to the Calculator title bar and click and hold the right mouse button. An outline of the window appears. Move the mouse outside of the window boundary and you will see the outline grow (and shrink if you move in the other direction). When you release the mouse button, the Calculator window is a different size than before. (Note: This command can also be found in the Window Ops menu.)
To get rid of windows you no longer want, click once on the kill icon along the top of the screen. The cursor becomes a skull and cross bones. Move the mouse to any position inside the Calculator window and click. The window should disappear.

Getting Started with UNIX

An operating system is a large program that coordinates all the resources for the execution of programs. UNIX is the operating system on the Sun Ultra-SPARCstations. UNIX contains lots of commands, a few important ones are introduced here. 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] rcduvall@teer8%

except rcduvall should be replaced by your login-id and the number may be different. If you make a mistake when typing a UNIX command, use the delete key or the arrow keys to correct it.

To make the font bigger and easier to read you can hold the control key down while pressing and holding the right mouse button while the cursor is in an xterm window. Choose large for an easier-to-read window.

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 within an xterm window, at the prompt type ~rcduvall/cps108/bin/setup. This runs a program that will set up some files in your directory to make it easier to use the programming tools we provide. Additionally, it creates a directory in your account, called cps108, for you to put your CPS 108 work. 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, please consult this page for more information on exactly what this command does.

In order for changes made by the setup command to take effect, you will need to logout and then log back in. To logout of your Sun workstation, click the logout icon at the top left of the window. Now, please log out, then log back in.

Creating and Traversing Directories

To do the work for the remainder of this lab, you will need to create a directory (i.e., folder) to contain the files for your program. In this course, we will follow a convention of creating a separate directory for each project within your cps108 directory.

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/c/rcduvall except your login-id should be the rightmost word.

To create a directory called bowling for storing new files related to this project, you will need to follow these steps:

Change into your cps108 directory by typing cd cps108. This command should not produce any output, but should move you from your home directory to the cps108 directory within your home directory. You can verify this by typing pwd again.
Create a new directory called bowling by typing mkdir bowling
To list your files and directories, type ls (think of this as shorthand "list"). You should see the directory you just created printed.
Change into your bowling directory by typing cd bowling

You are now ready to start working on a C++ program. The command to change directories, cd, lets you change directories relative to your current directory or absolutely to a specific directory. For example you can type cd ~rcduvall to change into Professor Duvall's directory. Type ls to see the files and directories contained there.

At any time, you can type cd (with no arguments) to return to your home directory. Now type cd cps108/bowling to return to your new project directory. Now when you type ls you will see there are no files in the directory, because you have not created any yet. Instructions for editing, compiling, and printing are given below. First, you will need to copy some files to your bowling directory. The copy command is cp so from within your bowling directory type (do not forget the trailing dot: "."):

      cp ~rcduvall/cps108/code/bowling/* .

Type ls to see that the files were copied. You should see a new file called Makefile and other files noted in the C++ Critique assignment. 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. We will go over the Makefile in a later course.

Programs: Edit, Compile, Debug

You will edit, compile, and run a C++ program in this section.

Starting the editor emacs

To type in your program you need to use an editor. To use the editor emacs to create a new file for your program click on the emacs icon. An emacs window should appear (please be patient!). You can use the arrow keys and the mouse to move around in the emacs 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.
The prompt for Find file: appears in the small minibuffer window at the bottom of the emacs window. You should also see a path which might be ~/ or ~/cps108/bowling/. 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 seuss.cc. To do so complete the path in the minibuffer so that it reads ~/cps108/bowling/seuss.cc 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 emacs 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 emacs 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 emacs window open. Unless you are logging off, there is seldom a reason to quit emacs. 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 emacs 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 emacs 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.

Compiling a C++ program

A compiler transforms your C++ code into machine readable code the computer can understand. Programs can be compiled from within emacs as well. To compile from within emacs:

Use the Compile option under the Tools menu.
The command make -k, which appears in the minibuffer, is the default compile command. For most C++ programs, this will be sufficient. Go ahead and hit return. It may take a while for the program to compile, but you should see an emacs sub-window with an indication that something is happening.
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:

     seuss.cc:5: unterminated string or character constant
     seuss.cc:5: possible real start of unterminated constant

This message tells you the name of the file (seuss.cc), 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 ";" and then compile the program.

When the program has been successfully compiled continue with the next section.

Execute your program

Compiling your program creates a new file with the same name as your source file (in this case seuss.cc), but without the .cc extension. This new file is executable, meaning it can now be used as a UNIX command.

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

bowling

To run any executable program, type its name in your terminal window, so type bowling to execute this program.
You can type ls -l to see how big the files are and when they were created.

To conserve the limited space in your account, you may want to get into the habit of removing the executable program (which is really big) when you are finished with the assignment (since you can always re-create it by recompiling the source code). To do this, type rm bowling to remove the executable.

Print a copy of your program

To print a file, just type print filename . Thus to print the file game.cc, type print game.cc.

The print command sends your file to the printer in the room you are currently in. If several people try to print at the same time on the same printer, the print jobs are queued and printed one at a time. To see where in the queue your job is type lpq followed by -Pname where name name is replaced by the printer name. In Teer 106, the printers are in the back of the room.

If you want to specify a specific printer, use the lpr command. There are two printers in Teer 106, named teerlp1 (the last three symbols are lowercase L, p, and the number 1) and teerlp2. To print any text file use the lpr command, specify the printername (prefixing it with -P , specify the file is a text file by -Fl (with lowercase L here) and type the file name. To print your program game.cc on the printer teerlp1, type

     lpr -Pteerlp1 -Fl game.cc

Note you can print your code in two columns (as in the C++ Critique handout) by giving print the extra argument -2.

Using CVS

For your projects in this course, you will want to consider using a revision control system like CVS. CVS is a program that manages your source code allowing you to "back out" of changes that you have made, or have several versions of your program available quickly and easily. CVS works by storing only the differences between versions of your program in a separate directory, called a repository. When you want to commit your changes to this repository, you issue the command cvs commit. You can also update your code or add new files to the project. One nice thing about CVS is that it easily scales to allow groups of people to share a common set of source code.

A more complete tutorial is available here. You are strongly urged to work your way through that tutorial, by making a CVS repository for your bowling project.

Logging out

To exit emacs, choose Exit from the File menu.

If you have not saved all your files, you will be asked at the bottom of the window whether or not to save a particular file. Type y for each file you want to save. When you are asked "Subprocesses are executing; kill them and exit?'' type yes and press Return. At this point, the emacs window will disappear. You should always exit emacs before logging out.

To logout of your Sun Ultra-SPARCstation, click on the logout icon at the top left of the screen.

You will see all the windows and icons disappear and you will be logged off. Never turn off the workstation!

Remember this document contains only a brief summary of useful commands to get you started. Refer to the other documents here to learn more.