Lab 1 Experiments: Programming Environment

Objectives

To gain some experience and understanding of

1.    A multiuser computer (loki)

2.    Unix, an operating system other than Microsoft Windows or MacOS

3.    The Unix interface called Command Line Interface or CLI  ( shell , specifically bash )

4.    To understand the difference between local and remote computing

Accounts

For the purposes of this lab, the computer that you are sitting in front of will be referred to as the local computer. In this lab you are going to use the local computer to connect to and then work on a remote computer. This remote machine is called loki. It's full Internet address is loki.cs.kent.edu.

Computers and operating systems that support many users at the same time are called multiuser systems. Since many people can use them at the same time each user has a separate account, identified by a username.

Each of you have your own account on the remote computer loki. Look up your username at  loki usernames

Your account will be protected from unauthorized access and use by way of a password. There is an initial default password which you will later change.

Remote Login

Computers used to be extremely large and expensive, and they produced great amounts of heat. So much heat was produced that they were put in their own large, air-conditioned rooms.

People would work at a station called a terminal. A terminal is a combination of a keyboard and a monitor. Out of the back of the terminal would be a long wire that would directly plug into a port on the computer (in the large, air-conditioned, room). The monitor could only display characters/text, and the only input device was a keyboard, so people would use a Command Line Interface (CLI) to interact with the computer. Thus named because one typed commands on a single line.

Not many people use a terminal anymore to do any useful work at the computer. In general they sit at a local computer and use it to work on a remote computer over a network.

A shell is a piece of software which provides a user interface to the computer's operating system, so that we may enter commands. There are many ways of accessing the shell on a remote computer from a local computer, including two programs called  telnet and ssh. The remote computer would run  telnet and/or ssh server software, and the local computer would run a telnet and/or ssh client software. We interact with the telnet client software on our local computer and it sends requests to the corresponding server software on the remote computer. Most multiuser computers run one of these server programs so that users can connect and use the machine.

As an aside, you have probably used and have on your home computer several other pieces of client software. You use an email client program (Outlook Express, Mozilla Thunderbird, Netscape's email client) to access an email server to retrieve and send mail. Your web browser contains a web client which makes requests for html and other documents from a web server.

The shell access client software (the one running on your local computer) gives you a terminal window that along with a keyboard behaves the same as the old monitors used in the original terminals.

Shell access, such as through the ssh or telnet  program is a simple and low-bandwidth way of connecting to a remote computer. Low-bandwidth means that only a small amount of information is transferred per second. It doesn't require a fast connection to the remote computer, and a client program can be run from any computer that is connected to a network, even if both computer are using different Graphical User Interface's (Windows, MAC OS, X-Windows etc.) or not using a GUI at all.

ssh

Although we discussed two ways of shell access to a remote computer, telnet and ssh we are only going to use ssh.

Using ssh

You are going to use an ssh client program from the local computer in front of you to access your account on the remote computer loki.

Record the steps that you take following these instructions. Include what you saw and what you typed in. If you had to repeat a step note this in your Lab Notebook.

To use ssh from MS Windows in the Lab:

At this point you should be connected to loki and on your account.

Note: You may download a free Windows compatible version of the SSH client program here SSHSecureShellClient-3.2.9.exe . Just click on the link Local Copy or Official Mirror Copy and Save the file on your machine. Once downloaded, the file may be installed by double-clicking on the name or icon. Once installed on a PC, this program will allow you to access your loki account over the internet.

Similar programs that support SSH are CoreLite, and PuTTY, which can be freely downloaded. Just click on their link.

Changing your password

When you get access to an account for the first time on of your first tasks is to change your password. Start thinking of a password now that you can remember. The password must be at least 6 characters long and include at least one digit. Of course, don't write it down in your lab notebook, but keep it in a safe place and don't let anybody else know what it is.

To change your password, at the prompt type:

passwd

and press the Enter key. The system may be slow to respond at times. Wait for it to prompt you and follow instructions. Pick something you won't forget that has at least one digit or uppercase character in it. If the password does not meet the current security guidelines, you will be asked to enter a different one. When you enter your password, it will not appear on the screen.

Your password can be changed any time you want. However if you forget your password you need to contact the system staff (at Kent!!!) through your Lab instructor and CSI coordinator to get it fixed. This takes almost 2 days!!!! so...Do write down your password in a safe place (NOT in the Notebook!). Do not give your password to anyone.

Leave this window open for the rest of the lab. We will get back to this window again. However you must remember to logout at the end of this lab to avoid that other people can have access to your data.

loki

The machine loki (loki.cs.kent.edu) is a PC running the linux operating system. The linux operating system is the newest member of the family of UNIX operating systems.

The different versions of the UNIX operating system were created by many different companies, such as AT&T, IBM, and Sun, running on many different kinds of computers from embedded computers (computers embedded in other devices) to mainframes. The majority of computers that form the backbone of the Internet are running some form of the UNIX operating system.

The core program of an UNIX operating systems is called the kernel. The linux kernel was originally written by Linus Torvalds when he wanted to use UNIX on his PC.

The linux operating system is an open source project. Essentially this means that all of the source code (the computer code written in a high-level language) is available to anyone who wants to use it. Companies and people can take it and extend it as long as they make their extensions also available. In fact, most of the software running on loki is open-source. At this point many companies, such as IBM, contribute source code to linux, All of it is available for free.

Installing and configuring the linux kernel is not particularly easy due to how flexible and powerful it is. To make linux easier to install commercial companies have come up with linux distributions that include the kernel and other software. Examples include CentOS, RedHat, Debian, and Mandrake. The linux distribution used on loki is Red Hat Enterprise 3. These distributions are also freely available for download from these companies. However people often buy one of these linux distributions because of the convenience, manuals, and support. A linux distribution on a CD can be copied and distributed freely.

The linux kernel is only part of what an operating system needs. Utility programs, graphical user interfaces, development environments and even application software is also needed. Much of the basic utilities that can be used with Linux are provided by the GNU Project, and the rest of the needed software is provided by other open-source projects. This combination of the linux kernel and supporting software is referred to as GNU/Linux, however many people just call it linux.

The ideas of open source software seem mysterious to some people. They don't understand why people or companies would give away their source code and not charge for their product. One of the best introductions to these ideas is The Cathedral and the Bazaar.

Using a Shell

The program ssh provides you a terminal window to a remote machine. This terminal window give you access to a shell program which provides a CLI (Command Line Interface). This shell program provides a user interface to the operating system, in which you use the keyboard to type in commands and view things using a text display.

The shell gives you a prompt and waits for you to enter a command. After you enter a command it carries it out and then returns to a prompt again.

There are many advantages to using a shell. The shell commands allow more options and are more sophisticated than using a windowing system. The shell commands, especially complicated ones, can be entered more quickly. Also long series of complicated shell commands can be easily automated.

People who work at setting up and maintaining computer systems often use a shell to do their work.

Using a Shell on loki

Here are just some of the commands that the shell on loki will let you use. Type in each command and record the command and what you observed. Each command is actually a program. Show your activity by copying the data in the notes (or by taking a screenshot of the window)

whoami

who

w

uptime

quota -v

Enter the command to see who else is on. Record the command that you used and the usernames of at least 3 other users.

Using the Secure File Transfer Client

The program ssh provides you a terminal window to a remote machine that can be used to transfer files from your local machine to a remote machine (e.g. loki) and vice versa. The SSH File Transfer Client window is the GUI (Graphical User Interface) terminal window for the file transfer.

Open Program--> Accessories --> Internet Tools --> SSH File Transfer Client  (on other machines, such as the one at your home, this program can be located in a different directory. Use the Search to locate it).

Click on Quick Connect and connect to loki.cs.kent.edu. Insert your password and click Connect.

The SSH File Transfer Client window is split in two parts: the right hand side half-window displays the content of the remote machine (i.e. loki) while the left hand side half-window displays the content of your local machine. When you connect to the remote machine, you will see that he right hand side half-window turns from gray (incative) to white (active).

You can view each single folder of your local machine as well as those of the remote machine. Practice a file transfer from your local laptop to loki. Just drag the file from the left hand side of the window and drop it on the right hand side. The file will not be removed from your local machine, but a copy will be made on the remote machine. When files are on loki, you can access them from any place as long as you have an SSH program to access remotely the loki machine. Record in your Notebook a snapshot of the SSH window after the file transfer.

Managing Files

For this section you will need both a terminal window to enter CLI commands in, and the SSH Secure File Transfer to see the content of the File Manager. You will go back and forth between one and the other.

File Information

Data is organized on computer systems into files. We use applications to create things such as research papers, email, web pages, Lab Reports, etc. that are stored as files. Much of the work that we do at the computer has to do with manipulating files.

With your terminal window, type in the following commands and record what you find in your Lab Notebook:

ls

list the files in the current directory

ls -a

list all the files in the current directory

ls -al

list all files in "long" format, show additional information

Now look at your files using the file manager SSH Secure File Transfer. Press the blue chasing arrows from the menu on the remote side to refresh the screen. You can get a detailed view of your files by clicking on the folder to open a folder and then using the folder with the back arrow from the menu to move downward and upward, respectively, in the hierarchy of the folders.

Deleting and Creating Files

Use an editor, such as Text Editor available in the menu such as Wordpad or Notepad (under Program--> Accessories) and create a text file on your local machine. In the file write the list of the courses that you are taking this semester. Save the file with the name "MyCourses.txt".

Locate the file under the SSH File Transfer Client window in the local machine (if you do not see your file, look for the chasing arrows in the Toolbar of the SSH File Transfer Client to refresh the window) and transfer the file remotely by dragging the file from the left hand side of the window to the right hand side of the window.

You will see that the file is now on loki.

Go to the SSH Secure Shell and use the command ls to check that the file is effectively there. (Be sure to be in the correct folder where you have transferred your file, otherwise use the command cd to go up or down in the hierarchy until you locate yourself in the correct folder. If you do not know how to proceed, ask your instructor).

Record in your Lab Notebook whether the SSH Secure Shell shows this file being created.

If we want to remove a file we can use the command:

rm MyCourses.txt

deletes the file "MyCourses.txt"

Type in the command and then use the command ls to see if it is there.

Go back to the SSH Secure File Transfer and refresh the screen with the blue chasing arrows.

Record in your Lab Notebook if the file manager shows this file any longer.

Files can also be deleted/removed by being in the SSH Secure File Transfer by selecting them and pressing the cross in the top menu.

Directories

Files are organized into directories. A directory in the CLI corresponds to a folder in the graphical user interface. This allows related files to be grouped together which makes them easier to organize for our use and for security.

In the CLI, to reach a file's location it is necessary to know what directory/folder it is in, and what directory that directory is in. and so on and so on. This is called the path to the file.

At any point in order to figure out the path to the directory we are in we can use the command:

pwd

"print working directory", shows the directory you are currently in.

In the file manager of the SSH Secure File Transfer the working directory is shown at the top in the menu.

Creating a Directory

To create a directory we can use the command:

mkdir CS1

create a directory named CS1 in the current directory.

Since you are hopefully in your home directory (you can use the command pwd to check) this will create a directory named CS1 in your home directory.

Note that file and directory names do not include any spaces.

To see what happened, use the command ls to see if the directory was created.

Record in your Lab Notebook whether the directory created is seen there also.

Moving to a Directory

Now we want to work in the CS1 directory. The easiest way to do that is to change our current directory to the CS 1 directory

You can use the following command to do that:

cd CS1

Use the command pwd to check that you are in the right directory.

Record in your Lab Notebook whether the file manager of the SSH Secure File Transfer changed to the subdirectory also. If not, double click on the name of the directory to go in.

Record in your Lab Notebook the file path that appears in the Location text-field of the SSH Secure File Transfer in the top menu.

Go back to the SSH Secure Shell. For demonstration purposes we would like to create a file in this subdirectory. We can use the following command to do that:

touch anewfile

creates an empty file called "anewfile"

Record in your Lab Notebook what is in the directory by using the command to see what the touch command did. Also check the file manager SSH Secure File Transfer to see if it is there.

Moving out of a Directory

In each directory there are always two special files. One has the name "." (yes, a single period) that is the current directory. The other has the name ".." (yes, two periods immediately after each other) that is the parent directory.

Before we show this, Go back to the SSH Secure Shell and record in your Lab Notebook the directory that you are in by using the command pwd

Now we want to move out of the subdirectory CS1 and back to our home directory. We can do this by using the command:

cd ..

".." denotes the parent of the current directory, the directory the current directory is in.

Now record in your Lab Notebook the directory that you are now in by using the command. Also, use an command to get your bearings.

Record in your Lab Notebook whether the file manager of the SSH Secure File Transfer changed its current directory. If not, you can move back up by clicking the folder with the back arrow in the top menu.

Home Directory Shortcuts

Return to the SSH Secure Shell. You can move directly to your home directory, no matter where you are at, by using the command:

cd

changes to your home directory.

You can also directly move to another accounts home directory. For example, we can move to the account llaguer0 home directory by using the command:

cd ~llaguer0

changes to the home directory of llaguer0 .

Change to the home directory of llaguer0 by using the command shown above. Record the path of their home directory by using the command

pwd

Record in your Lab Notebook what a person using another account would have to enter to move directly to your home directory.

Now move back to your home directory.

cd

An Example

Open Notepad on your local machine and type the following lines of code:

#include <iostream>
using namespace std;

int main()
{
cout << "Hello!" << endl;
cout << "Welcome to my class!" << endl;
return 0;
}

Save the file as hello.cpp. Now transfer the file from your local machine on loki using the SSH Secure File Transfer. Go back to your SSH Secure Shell terminal window and check the content of the file by using the command:

more hello.cpp

You will view the content of hello.cpp

This file is actually a program written in the C++ language. We can compile the program by using the command:

g++ hello.cpp -o hello

The command uses the program (compiler) g++ to compile the C++ program file hello.cpp in the the executable program called 'hello'. The executable program will be created in the current directory.

Check what files were created by using the command ls. You can also refresh the file manager of the SSH Secure File Transfer window to see the file presence (the refresh button has 2 arrows chasing each other). Record in your Lab Notebook the size of the files hello.cpp and hello

This is a program that can be run by using the command:

./hello

run the program in the file hello in the current directory.

Record in your Lab Notebook what the program did when it was run.