CSCI 160 Lab exercise 1: part 1

Phase I: intro to the labs/linux

Get logged in to your CSCI account
(you'll do this every time you want to work on one of your CSCI labs)
1. Using your account id ( available from the course instructor), follow the instructions below login to the windows machine using your regular VIU login credentials, open a web browser, and open the course lab page csci.viu.ca/~wesselsd/courses/csci160/labs.html
   Follow the link to lab exercise 1, read the notes for today's exercise, and follow the link for part 1.

2. Open the windows powershell either by right clicking the Windows icon in the lower left or by using the keyboard shortcut Windows Key + X
   This will open a new text window through which we'll connect to the CSCI department linux servers.
   Most of the remaining instructions below will be carried out through this new text window

   Feel free to customize the properties of the powershell window, the defaults aren't pretty!

3. The program we'll use to connect to the linux server is called ssh (secure shell).
   Using the linux username provided for your account, use the following command to connect to our server (the -l is a lowercase L, not a 1)
   ssh -l yourusername csci.viu.ca
   You may be asked if you trust the RSA key for this server, reply yes.
   You will then be prompted to enter your password, enter the one provided on your account sheet.
   Nothing will appear on screen as you type, keep typing anyway and hit enter when finished.
   (Simply try again if the password was mistyped.)
   Once connected, you'll see the message of the day for the server, and you may be prompted to pick a new password. Pick something secure that you can remember, and follow the instructions given.

   Instructions on how to change your password later, or how to deal with a forgotten password, are provided on the technotes page.

   Through the ssh connection we have established, we can now issue linux instructions to the csci server and run programs on that server. For the moment, all our interaction with the server will be through text commands and the text responses the server provides.
   (Later in the term we'll discuss the use of X2Go to allow you to run graphical programs on the linux server and have the results display on your Windows lab machine, details can be found through the technotes page, along with instructions for other platforms.)

4. Starting with some basic linux:

   • Whenever you connect to the linux server you'll be started in the home directory (like a Windows folder) for your account.
     Enter the command ls to list the current contents (file and directories) of your account.

   • You can create new directories using the mkdir command and the name of the new directory. Try creating one named csci160:
     mkdir csci160
     Linux takes a "no news is good news" approach to command success: if the command succeeded it will simply give you a new prompt.

   • If the command succeeded, it will have created the new directory inside your current directory. Try the ls command again to see if it shows up.

   • We can move from one directory to another using the cd command and the name of the directory we wish to go to, try
     cd csci160
     (by default it assumes you're giving the name of a directory inside the current one).
     If it succeeded, try ls again, which should show the directory is empty so far (unless you've taken the course previously).
     We can display the full name of our current directory location using the command pwd (for print working directory).
     We can go back "up" one layer, in this case to our home directory, using cd ..
     We can also jump directly to our home directory from anywhere else using the command cd (with no arguments)
     Use either of the two approaches to get back to your home directory, then try pwd and ls again to confirm you are where you want to be.

5. Copy a special makefile from the instructor's account to your home directory.
   Makefiles allow us to bundle up sets of linux commands, and run them through a program called make. This semester I'll be providing a variety of makefiles to simplify the process of obtaining, compiling, and submitting your lab exercises.
   The first makefile belongs in your home directory and will be named make160. Instructions for obtaining using it are as follows:

   • There are two slightly different versions of the file, based on which lab section of the course you are enrolled in. Be sure you use the correct command based on your lab section.

     These files will probably not be available until shortly before the lab on Monday Sept. 13th.

     To copy the file from the instructor account to your own, first make sure you're in your home directory (e.g. using cd) then issue the following copy command precisely:
     Monday lab section: cp ~wesselsd/make160-01 make160
     Friday lab section: cp ~wesselsd/make160-02 make160
     Use the ls command afterwards to check the file is present and named correctly.

   • We'll now run the make program, telling it which makefile to use (i.e. make160) and what we want it to create. In this case, that will be a directory csci160/labex0 (i.e. a labex0 directory inside your csci160 directory).
     The full command to do this is
     make -f make160 csci160/labex0
     If the command is mistyped then you'll likely get a series of complaints from the make program, simply check the precise command and try again.
     If the command is successful then you'll see a series of git and ssh responses as it sets up a variety of files and directories based on the instructor's git repository. (Git is a tool heavily used for version control and for sharing code bases.)

     What is the makefile doing right now? The instructor has created a special directory containing the starting files for lab exercise 0, including starter code and its own makefile, which in turn allows you to automatically compile and submit your C++ code for lab exercise 0. If you'd like a look at a makefile's content you can dump it onto the screen using the cat command and the filename, e.g. cat make160 If you're curious about the workings of git for assignment submission (i.e. what the makefile is doing for you) there is a short rundown linked from the technotes page.

   • Try compiling and running the starting code

     • Change from the current directory into your labex0 directory and see what's there:
       cd csci160/labex0
       ls
       Hopefully you'll see files named makefile and labex0.cpp (the starting C++ source code file).

     • Try using make to compile the program into an executable named labex0 (note that those precise names are encoded in the makefile, so spelling and capitalization must be exact):
       make labex0
       The make program will show you the commands it is running, in this case a g++ command to compile the program.
       If successful, ls should now also show a file named labex0, the newly created executable.

     • Hopefully the file contains no errors (I didn't intend to include any), so it should compile cleanly (no error or warning messages) and we can try running it:
       ./labex0
       At the moment the program should simply display a small message then end.

   • Try editing, compiling, and running the starting code

     • Since we're just working within the text window for now, we'll need to use a pretty basic editor for modifying the .cpp file.
       We can start with one named pico, later in the term we'll discuss better (but more complex) editors.
       To edit a file we use pico and the filename (if the file doesn't exist yet then it creates a new empty file with that name).
       pico labex0.cpp
       You should now see the C++ source code for the program, and at the bottom of the window there should be a couple of lines telling you the pico command shortcuts, using ^ to indicate the control key.
       Change the message inside the printf string to include your name, then save the file using ^O (control and o), and hit enter when it asks for confirmation of the filename.
       Exit the editor using ^X, which should return you to the linux prompt.

     • To compile, use the make labex0 command
       If it gives error messages then we broke something editing the printf statement -- see if you can figure out the nature of the problem based on the file content and the g++ error message, but don't hesitate to ask for help!
       Keep going through the edit/compile cycle until it compiles cleanly, then try running the updated executable to see if your new message appears correctly
       ./labex0

     • Try submitting the exercise

       • We'll use a make command to turn in your work:
         make submit
         If successful, you'll see a variety of status updates as it uses the git version control program to copy your updated work to a location where the instructor can obtain/mark it.

         Each time you do a "make submit" git is used to store the current state of the directory and copy it to the instructor-accessible location. The instructor can only see changes after you submit them, so be sure to do a make submit after your final set of changes for any lab.

   • Log out of your linux account
     Enter the command logout
     After logging out, you'll be back in powershell, feel free to close the window.

   ---

   Extra step if you have time

   Let's try quickly running through the cycle one more time, to demonstrate that the labex0 files will still be present on the linux server the next time you log in. An abbreviated list of steps is given here, refer to the instructions above if you can't remember the command for a specific step

   • Open the powershell window

   • ssh into your csci account (using your new password)

   • cd into your csci160/labex0 directory

   • try an ls to see the files that are present

   • edit the labex0.cpp file again, tweak the printf string a bit more

   • save and exit the editor

   • compile the program using make (edit/save/compile until it is clean)

   • try a test run of your revised program

   • submit the revised version (it's ok to submit multiple times)

   ---

   Note that you must be in the correct directory, e.g. csci160/labex0, whenever you are working on a lab exercise, otherwise the necessary makefile and source code files are not present. If you're unsure which directory you are in, enter the command pwd If you find you are in an incorrect directory then you can jump directly to the labex0 directory using the following command: cd ~/csci160/lab0