Assignment 1 – Introduction to Linux

COMP 3411: Operating Systems 1
Assignment 1 – Introduction to Linux (5%)

Instructions
You need to be knowledgeable of a typical operating system to understand the
functionality of how it works. Windows is not a typical operating system as it has
both operating system characteristics and well as user functionality mixed together.
To have a better understanding of what an operating system is we are going to do
some simple work on a Linux system this term. Assignment 1 is a simple
introductory tutorial on the basics of Linux, including some basic programming in
Java and C. We’ll be using the Linux machine for programming at times through the
course, so it is important to a basic understanding of the Unix basics.
You must submit Java, and C files and screen shots that show how your
program works. Refer to the marking criteria at the end of this document.
UNIX/Linux
Developed in the early 1970s at Bell Labs, UNIX was created as an "open" operating
system that provided end-users the ability to extensively customise it, as needed.
Because of its portability and low distribution cost, UNIX became very popular with
universities, researchers, and businesses. It was eventually ported to most
mainframe and mini-computers.
(Note: Although first coded in Assembly Language, UNIX was
developed with the C programming language in mind. As long
as a C compiler is available for a given platform (CPU and bus
architecture), UNIX can be compiled for it!)
For microcomputers, full UNIX is far too large (resource-wise). To run on these
machines, different flavours of UNIX were introduced, such as FreeBSD, SCO-UNIX,
XENIX, and Minix (Mini-UNIX). In 1991, Linus Torvalds took the Minix kernel and
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crafted it for the i386 platform (based on the Intel 80386 CPU architecture, which
includes all processors from 80386, 80486, and Pentium I/II/III/IV CPUs). He named
the new, non-commercial flavour "Linux" (Little UNIX), and released it freely to the
computing public for further development.
(Note: So why did Linus develop Linux? Most PC OSes were
either not complex enough or too expensive (or both) for what he
needed while going to school. The university's mini was shared
by all students and faculty, with never enough available usertime,
time for Linus to just "play." Wanting the power of the mini's
OS at home...and the rest is history.)
Today, many companies release their own Linux distributions ("distros") that
include special configurations, software collections, and programming languages,
with drivers for most new buses and devices (USB, IEEE1394, scanners, LCDs, etc.).
For all practical purposes, Linux is essentially the same as UNIX. Mostly all
usercommands, application programs, and general concepts apply to Linux as they
do UNIX. Aside from some administrative differences, users are equally
comfortable in either operating system.
(Note: Linux is part of the GNU Software Development
(GNU"GNU is Not Unix") and most Linux open-source software
is part of the GPL (GPL-"GNU Public License").
"Opensource"—the source code is open to all.)
So, which is the best Linux distribution? With so many available, and each almost
specialised for specific tasks and environments (only all-purpose, or "generic,"
releases get media attention), the question should be: which Linux distribution best fits
the current needs? For the moment, the answer is a personal one.
CLI/GUI
UNIX is a command-line interface (CLI), with interaction accomplished through a
"shell" (of which there are many) that behaves like DOS's command line (or
Window's Command Prompt). Many UNIX commands are similar to DOS (since
most DOS commands actually originated from UNIX). Directories function almost
identically in UNIX as they do DOS, except for advanced security and the concepts
of "symbolic links" and "ownership."
Not to be outdone by MacOS or Windows, UNIX incorporates a graphical shell
called a window manager to provide GUI features. Window managers use
XWindows: a library of graphic functions providing graphical interfaces similar to
Windows. Sitting atop X-Windows, the window manager provides a similar userand application-interface to Windows and MacOS.
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Future Focus of UNIX/Linux
Most computing professionals view UNIX as a "workhorse operating system,"
meaning that it is dependable, stable, and strong, but not very pretty, and this
description has carried over to Linux. Most servers on the Internet, and in large
businesses, run a flavour of UNIX rather than another OS; even Microsoft maintains
a set of *NIX-based machines for some web-services (although they don't advertise
this fact, of course).
But in providing a comfortable, intuitive environment for the average, end-user,
Linux requires much improvement for installation/set-up and interaction tasks
(relating equally to software and hardware). With periodic updates to the kernel,
GUIs (window managers), and methods for installing new hardware, Linux has
recently found itself being prematurely promoted as a "desktop operating system"
rather than just a server-class operating system.
So the question is: will Linux replace Microsoft Windows and Apple MacOS as the common
desktop operating system?
Many pro-Linux groups enjoy dreaming such, but the reality is that Windows and
MacOS will continue—at least for the short term. Yet Linux has changed how Apple
and Microsoft design their operating systems. From gaining blatant X-Windows
"look-and-feel" aspects, to more reliable operating system cores designed around
kernel-level interactions rather than linear-polling structures, Apple and Microsoft have
shifted towards the UNIX direction.
Topics of this assignment
The breadth of topics related to learning UNIX/Linux is far beyond this one
exercises. The goal of this assignment is to introduce the *NIX-style (as it is called)
of operating systems, and help summarise the important and essential aspects.
1. The command shell through a terminal window
2. Basic command syntax and purpose; access to built-in help.
3. Directories: creation, navigation, and destruction; copying/moving files in
directories.
4. "Who's logged on?" and file/directory ownership.
5. Editing files and language compilers: creating simple C++ and Java programs.
Observations and Tasks
Part 1: Getting Started
To access the TRU Linux server:
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a. Machine name is: cs2.tru.ca
b. Set port to: 2200
c. Connect using username and password obtained from your Open Learning
Faculty Member
Note: You may need to install additional software to access the Unix server.
 [Windows Users]: To connect to the TRU Linux server, install PuTTY and
WinSCP following the instructions provided below.
 [Mac Users]: You can use the built-in terminal software on your Mac to
connect to the TRU Linux server. You may use any file transfer program
of your choosing to move files between your Mac and the TRU Linux
server.
 [Linux Users]: Connect to the remote host using: ssh -p 2200 -l
[username] cs2.tru.ca. Use the sftp program to connect to the TRU Linux
server on port 2200.
Additional software required for Windows users:
1. PuTTY is an X Window client. A free download of PuTTY is available at:
http://www.chiark.greenend.org.uk/~sgtatham/putty/download.html.
2. WinSCP is a secure file transfer program. A free down load of WinSCP is
available at: http://www.winscp.com/
Part 2: Terminals and User Interaction and Basic commands
1. To open a terminal window (also called a "console" or "shell window"), click the
taskbar icon that looks like a computer monitor.
2. Command line interaction with Linux is done through a shell, which performs
the same function as MS-DOS Command Prompt in Windows: to provide a
"command line interface" to the user.
3. Common shells: Bourne (bsh), Korn (ksh), C-shell (csh), tcsh (from C-shell),
and zsh (from Korn shell), with the most popular Linux shell being bash
(Bourne again shell).
Along with command interaction, shells provide complete programming languages
(programs written in shell languages are called shell scripts).
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Although not fully featured as common programming languages (C++, COBOL,
Java, Pascal), shells have almost as much capability as other scripting languages such
as VBscript or Javascript.
4. There is a small set of often-used commands that must become familiar to all
users. These are related to file copying/moving, directory navigation, and
logging in/logging out.
5. Obtain a listing of files in your directory, type: ls To see all files (including
hidden files), type: ls –a
For a longer, detailed display, type: ls –al
(Some Linux even provide dir command, similar to DOS; try it.)
6. To check if another specific computer is available, use the Internet ping
command, type: ping 192.162.22.110 (Guru), and www.tru.ca (TRU
Webserver)
Note: <CTRL-C> can exit almost any command line application.
If this doesn't work, try quitting by just pressing the "Q" key.
Part 3: Built-in Help
1. Most new Linux users (called newbies or noobies) find Linux very confusing
because so many commands must be learned: which command to use, and what
does it do. (this is a similar complaint of DOS)
Such as the strange sounding commands: mv, grep, and chown.
2. With hundreds of available commands (written by different people, over the
decades of UNIX/Linux's history), confusion can set in quickly. To help,
designers always include "online manuals" called man pages that index
[almost] every available command.
For programmers, man pages also include descriptions of key
C-functions for use in relating to the OS, such as scanf() and printf().
3. To use a man page for help, use the syntax: man command Use this method to
get help on the commands: date, grep, and top.
4. Another help method is to ask for condensed help directly from the
command (built-in help). The syntax is: command --help
5. Most Linux distributions also include the info command. This is a large
interactive, summary document of important Linux commands.
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Info is used alone or with a command, use the syntax: info command.
For newbies getting familiar with one of the help methods is a must.
6. If you have not done so already, obtain help for the commands you typed in
Part 2 (using one of the methods: man, --help, or info).
Did these commands have at least built-in --help available?
Part 4: Command Piping and Redirection
1. At the command line data can transferred from one command to another, or
redirect input/output from/to files. These concepts are available in most
operating systems because of the necessary programming required at the
command line level.
"piping" – pipe the output of one command as input to another;
"redirection" – redirect output of a command to a file, or file content as input to a
command
2. As an example of this technique, the following use more than one command
per line, moving data from one to another.
3. To locate all the files in the running Linux operating system, and load the
output into a buffer that you can scroll through (or page up/down), type:
locate / | less
Press 'Q' to quit the less command.
4. Output can also be sent to a file, rather than to the screen. To store a listing of
all the files in the current directory (or 'folder' for GUI users), type: ls -a >
files.txt
5. To examine the contents of the file, type: less files.txt
6. For a sorted listing of the files in the current directory, type either of the
following:
a) ls –a | sort | less or
b) ls –a | sort > files.txt , followed by: less files.txt
7. The screen might be a little messy at this point, and it would be nice to clear
the screen. To clear the CLI screen, type: clear Applying Piping and the cal
command
8. An interesting command is cal, which produces a calendar view of a year, or
just a month, for the range of years 1-9999.
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9. Get some help on the cal command and produce a display showing which
day of the week your birthday falls on in 2003, 2004, and 2055.
10. Determine the cal command to display only your birthmonth this year. Pipe
the output to a file called, mybirthday.txt
Use less to examine the mybirthday.txt file.
Part 5: Resource Identification and Environment Variables
1. A main concern for servers is the availability of resources—the fewer
resources available, the lower the overall system performance.
2. The following commands display the status of the essential resources
available on the server, try them,
free –o – memory allocation on the computer
df – free disk space on main partitions (shown as devices)
top – top running processes (measure of CPU utilisation); "q" to quit
date – current date/time (not a resource, but useful)
3. Each login session obtains its own configuration environment. To display the
current environment variables, in sorted order, type: printenv | sort | less
4. From this display, look up the values of the these environment variables,
home - path for user's home directory
hz - length of command history (previous commands used)
language - CLI interface language (keyboard, display characters)
logname - login name (default in this case is "knoppix")
oldpwd - previous current directory (see pwd)
path - directory path names to search for executing commands
pwd - path of current working directory (where you are now)
shell - directory path location for active shell program files
user - name of user logged in (usually similar to logname)
Part 6: Directories
1. Directories in Linux behave similarly to directories/folders in Windows,
except that Linux provides "symbolic links" (virtual directories pointing
elsewhere) and "owned directories" (belonging to particular users).
2. In Linux, all devices (drives) and every user directory "hang" off the root
directory (/). Unlike Windows, Linux does not have drive letters, only
directories, even different drives (or partitions) are treated as directories.
[The following steps guide you through a little directory exercise.]
3. In your current user-directory, create a new directory called "mydir," type:
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mkdir mydir.
4. Produce a listing with both ls and ls –l to see the directory you created.
(Note: As you work through the following, produce a listing after each command to
see how things change: ls –l )
5. Use the VI line editor to create the following file. Type: vi myfile.file
Type Shift I for Insert
Put the following in the file
Linux is really neat. Linux is different.
Linux is not Windows.
Hit Esc key to get out of insert mode
:w to write and then
:q to exit the editor
6. Copy the file into mydir, type: cp myfile.file mydir/myfile.file
7. Move the current file to another name (i.e., rename the file), type: mv
myfile.file other.file
8. Change into the new directory, type: cd mydir
9. Move the file from the subdirectory to the parent directory, type: mv
myfile.file ..
10. Change back to the parent directory, type: cd ..
11. With the subdirectory now empty, remove it, type: rmdir mydir
12. Remove the two files you created, type: rm *.file
Part 7: Writing a small program in C
(Ensure you are not in a root shell; root user should never develop code.)
1. Except for dedicated languages (such as for databases), there exists a Linux
compiler, or interpreter, for almost all programming languages.
2. With the popularity of UNIX (and its various flavours) for the last 25 years,
C/C++ has become the standard language for most all OSes.
3. Open a text editor to begin a new file, type: vi smallprogram.c
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4. Code the C program below. When finished, save and quit the editor.
#include <stdio.h>
#define MAX 40 // maximum name length
//function prototype
void display (char n[], int times);
//main function (does not need prototype) int
main (void)
{ char name[MAX]; // user's name
int loop=0; // number of loops
 printf ("What is your name? ");
gets(name); // get user's name
printf ("How many times shall I print it? ");
scanf ("%d",&loop); // read no. of times
 display (name, loop);
return (0); } // end of
main()
//function display (n)ame so many (t)imes void
display (char n[], int t)
{ int i=0; for
(i=0; i<t; i++)
printf ("%s ",n);
 printf ("\n"); }//
end of display()
5. Quit the editor and return to the command line window.
6. To compile the program and generate the executable, type:
gcc smallprogram.c –o smallprogram.out
(ignore the warning about gets() )
7. If there are syntax errors, edit the file again and fix them. To
run the program, type: ./smallprogram.out
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Performing a Screen Capture
8. When running a program, its output and user interactions can be captured
and sent to a file. This file can be brought into an editor, and then printed.
9. The script command opens a temporary shell and begins capturing (echoing)
the complete input/output user interaction to a file. To stop the capture, close
the file, and exit the shell, type exit
For example (user input is in bold),
_> script out.txt
Script started, file is out.txt
_> ./smallprogram.out
What is your name? Bob
How many times shall I print it? 3
Bob Bob Bob
_> exit exit
Script done, file is out.txt
10. Be warned that script captures all console input/output. For systems that use
an ANSI-graphic enabled user-shell, the script contains all console graphic
manipulations.
Part 8: Writing a small program in Java
1. Linux provides more than just older programming languages. New
languages also exist in Linux, such as: Java.
2. Use vi to code the following, and save it as smallprogram.java
import java.*;
import java.io.*;
public class smallprogram
{
public static void main(String[] args)
{
 String opinion = " likes Linux! "; char
first=' ', last=' '; // user's initials int
loop = 20; // number of times to repeat
 try
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 {
 System.out.print("Your first initial? ");
first = (char)System.in.read();
 System.in.read();
 System.out.print("Your last initial? ");
last = (char)System.in.read();
 System.in.read();
 }
 catch (IOException e)
 {
 }
 System.out.println("Repeating "+loop+" times.");
 for (int i=0; i<loop; i++)
 System.out.print(first+"."+last+"."+opinion);
 System.out.println();
} // end of main()
} // end of smallprogram
3. Quit the editor and return to the command line window.
4. To compile the program, type: javac smallprogram.java
5. If there are errors, return to the editor, and fix them. To run the program,
type: java smallprogram
Part 9: Finishing Up
1. Copy the Java and C programs, and the screen capture of the running
programs off the Linux machine and submit them with a cover page as
assignment 1.
2. Logout and close all windows.
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Assignment Marking Criteria Weighting
No syntax error: All requirements are fully implemented without
syntax errors. Submitted screen shots will be reviewed with source
code.
/5
Correct implementation: All requirements are correctly implemented
and produce correct results Submitted screen shots will be reviewed
with source code.
/5
Total /10