Description
1 Introduction
This laboratory is intended to give you some brief experience using the editing/compiling/file
management tools that are available in the Linux environment. You will not be required to do
any actual programming in this laboratory exercise. However, you will need to follow directions
exactly in order to complete the laboratory successfully. While there are usually two ways to
accomplish the tasks laid out in this laboratory (either via the windowing environment via point
and click or from the command line), we will use the command-line approach for most of this
lab.
2 Getting Started
Step 1: Obtain your username and password from laboratory teaching assistant. Do not confuse
this username/password with your OHIOID and OHIO password, the ones that you use for your
email account and for Blackboard. You will need both to successfully complete this laboratory.
Step 2: Log on to the workstation that you are sitting at using your CS username/password.
When you login for the first time, you may see an error message relating to the desktop.
Do not worry about it. Simply click OK.
Step 3: Once you have logged in you will see a toolbar on the left with some icons which look
familiar to you, including one for the Firefox browser and one for File management. The circle
at the top is the Search. Click on this. In the search text box type term to pull up the Terminal
icon. Then, using the mouse, drag and drop this icon onto the toolbar at the left. Now the
Terminal will be readily available every time you log into one of the lab machines. (You do not
need to log into the same machine every time because your desktop configuration and your files
are stored on the server and will “follow” you from machine to machine.)
Step 4: Click on the Terminal icon on the toolbar and continue with this lab.
3 Linux Fundamentals
Linux is an operating system just like Microsoft Windows and Mac OS. Linux is a multi-user
operating system. Each machine that you are sitting at may have multiple users. For these
laboratory machines, normally, only you will be logged into them. In order to see which other
users are using the machine that you are logged into, type
who
at the terminal prompt and hit “enter.” The Linux command shell (the terminal window that
you are using) and the windowing environment allow you (i) execute programs, and (ii) view
and manipulate files. The Linux file system consists of directories and regular files. Directories
2
are simply a “folder” where you place a collection of files. Directories may contain other
directories. These other directories are subdirectories of the bigger folder (parent). The root of
the entire file system is the directory /. The root of your directory is usually
/home/username, where username is your username.
3.1 Listing the Directory
From the terminal, you can display all of files (and subdirectories) in your current directory by
typing
ls
(You can also look at your current directory by using the windowing system. It’s useful to know
how to do both.) With the command ls you can list all of the files matching some pattern in
your directory. The wildcard character * can be used to denote any string of characters. So,
issuing the command ls *.cc will list all of the files in the current directory with the .cc
extension. Similarly, you can give ls the name of a directory to list. Issue the command
ls / to see what happens.
3.2 Working Directories
The Linux shell always keeps track of where you are in the file system. In particular, it
“remembers” the location of the current directory that you are working in. This is your
“working directory.” To see your working directory, type
pwd
This is the command for “print working directory.”
There are two “special names” for directories in the Linux shell. The first special name is “.”,
which denotes the current working directory. The second name is “..” which denotes the
parent of the current working directory.
3.3 Changing Directories
You can change between directories using the command cd in the Linux shell. To change to
a specific directory, you can issue the command “cd directory”. For example,
cd / changes the directory to the root of the file system. To get back to your home
directory, you can always type cd by itself. To get to the parent directory, simply type
cd .. The command cd . does nothing (why?).
3.4 Creating Subdirectories
You can create subdirectories by issuing the command mkdir. For example, the command
mkdir CS2400 will create a subdirectory in your home directory called CS2400.
3
3.5 Copying, moving, and deleting files
The commands cp, mv and rm copy, move, and delete files in your directory.
3.6 Manual Pages
To find out more information on a given Linux shell command, simply type
man command
For example,
man cp
displays the manual pages for the cp (copy) command.
3.7 Additional Linux Commands
Some other basic Linux commands that you can enter from your terminal:
• rm — delete a file.
• mv — move (rename) a file.
• more — display a file.
3.8 Lab Answer Sheet
After reviewing the previous sections, answer questions 1–8 on the lab answer
sheet. Don’t forget to write your GitHub user name.
4 Change Your Password
Place your cursor on the “terminal window”. One of the first commands that might want to use
is the following: Change your password by using the passwd command.
% passwd
passwd: Changing password for example
Enter login(NIS+) password: (ENTER YOUR OLD PASSWORD)
New password: (ENTER YOUR NEW PASSWORD)
Re-enter new password: (RE-ENTER YOUR NEW PASSWORD)
NIS+ password information changed for example
NIS+ credential information changed for example
Contact John Tysko if you ever forget your password. tysko@ohio.edu
4
5 Create Directories
The prompt that is being displayed will be the name of the workstation at which you are sitting.
To keep your space tidy we will begin by creating some directories.
Type mkdir 2400 make the directory 2400 under the current working directory
Type cd 2400 go into the new directory
Type mkdir Labs
Type cd Labs
Type mkdir lab1
Type cd lab1
This directory is where you should perform all of your work for this lab.
6 Useful Linux Constructs
The Linux shell has a number of useful features that allow you to manipulate the input and
output of files.
I/O Redirection:
Redirecting the standard output. You can redirect the output of any Linux command to an
output file (file.out in this example) instead of to the screen by placing the symbol
“>” in front of the output file name. For example, the following command will output a list of
the files in your current directory and save them to the specified file:
ls > file.out
Redirecting the standard input. You can redirect your program to take its input from a file
(file.in in this example) instead of from the keyboard by using the input redirection symbol
“<”.
myprog < file.in Pipes: ls | more Script: > script record.out
Script started, file is record.out
> ls
notes1.aux notes1.tex~ notes2.tex
> exit
exit
Script done, file is record.out
5
> more record.out
7 The C++ Compiler
The C++ compiler in our Linux environment is free software developed by the Free Software
Foundation (GNU).
The program is g++. To compile a C++ program using g++, simply type
g++ -Wall program.cc
If the program file program.cc is complete and correct, the g++ compiler will produce an
executable file called a.out. To run your program, simply issue the command
./a.out (Note that . is the current directory.)
The g++ compiler has many options. To see them, issue the command man g++. You may
ignore most of these options for now. However, the following options to g++ may be useful to
you.
-g: This option compiles your program with useful debugging information included.
-o outfile: This option places the result of the g++ in the file outfile. This is one way to
change the name of your executable from a.out to something else.
-c: This option stops compilation at the object file level. We will use this option later.
-O: Optimize the code. This option is incompatible with the -g option.
-Wall: This option shows the user all warnings messages that the compiler detected.
7.1 Lab Answer Sheet
Complete questions 9 – 11 on the lab answer sheet.
8 Problem Solving
The next few problems will give you some practice using the Linux editors, the compiler, and
some other useful commands.
Writing and compiling a simple C++ program
First, go to the lab1 directory you created. Use an editor that you feel comfortable using.
Good choices are: code, atom, nano, gedit. In the terminal window you can type:
code firstProgram.cc
This will start the VSCode editor with the file name specified.
6
All real programmers meet a new programming environment with a “Hello” program. We will
now write such a program in our new environment.
//* * * * * * * * * * * * * * * * * * * * * * * * * *
//
// program:
//
// Name :
// Date :
// Email :
//
// Description: This program prints a message
// to the screen.
//
// * * * * * * * * * * * * * * * * * * * * * * * * * *
#include
using namespace std;
int main( )
{
cout << “Hello Me! \n How am I today? \n”; //You can be creative with your message. return (0); } 1. Name the file whatever you wish—an appropriate choice would be lab1.cc. You can use any one of the following extensions: .cc, .cpp, or, .cxx 2. Compile lab1.cc by using the command g++ -Wall lab1.cc 3. Issue the command ls and answer question # 12 on the lab answer sheet. 4. Run the executable by typing ./a.out (see the output on the screen) 5. Use I/O redirection to save the results of this command as follows. You can redirect the program output to a file called lab1.out instead of to the screen. ./a.out > lab1.out (warning: do not redirect to lab1.cc)
6. Issue the command ls and answer question # 13 on the lab answer sheet.
7. Type more lab1.out to make sure that you produced the correct output.
8. Create a GitHub account using your school’s email and edit your profile to enter your
full name.
9. Answer the remaining questions on the lab answer sheet.
