Operating System Lab Manual

Laboratory Activity 1
Name: __________________________________ Date: _____________
Unix Basic Commands
1.0 Unix / Linux Command Line Interface (CLI) Basics – Basic Commands
This section of the course provides a discussion and hands-on guide on the basic CLI commands in Unix/Linux. The
basic CLI commands are: how to log-in, log-out, interpreting the command prompt, how to enter commands, basic file
commands and management, and simple file permission. The objectives of this section are:
• Familiarize the students on how to gain access to a Unix/Linux server.
• Familiarize the students on what is the prompt and how to enter commands.
• Familiarize the students on file identifiers and, relative and absolute file names.
• Familiarize the students on basic file commands and management.
1.1. Logging In
To access a Unix/Linux server, a Telnet or SSH client software can be used to connect to the server. Most operating
system today has some form of this software like “putty.exe”. A login prompt for a Unix server can look like:
Login: <username>
Password:
Before you try to log-in to a Unix server, ask your instructor for a user account, and the IP address or server name
where your account is valid. After acquiring the user account and the server you are assigned to, accomplish the
following:
Step 1 On your Windows operating system, use an ssh client program to connect to the Unix server. Using the
“putty” client program, enter the IP address or name of the Linux server in the “Host Name” text box and
click the “Open” button.
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Step 2 At the login prompt, type your assigned username and password.
2a. Were you able to login? How were you able to login?
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2b. Did you have a user account when you logged-in?
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2c. What is the IP address or server name of the Unix server you logged into?
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1.2. The Command Prompt
After you have logged-in, notice that a prompt will appear on the screen. A prompt is an interface that allows user to
input commands. Different shells use different faces of prompts (shells will be tackled later in the course). In this
server, you will be greeted with:
Notice the different parts of your prompt. For the example prompt, it has displayed the username, current directory you
are in, the computer name and the prompt sign.
Step 3 Write down the prompt on your screen.
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3a. Is your username displayed on the prompt? What is your username?
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3b. Is a computer name displayed on the prompt? What is the computer name?
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3c. What is the prompt sign on your screen?
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1.3. Entering Commands
Commands can be entered to the Unix server via the command prompt. This is usually done by typing a series of
characters after the prompt sign. A usual format in entering commands is:
[dwight@netopsy1 greg]$ command <options> <argument>
Options for the command are switches that tell a command to do something differently. Arguments are information
sometimes needed by the command to be able to execute properly. Most of the time, options and arguments are not
needed in a command.
There are also commands wherein you do not need to type anything. These commands are: ctrl-c, ctrl-d, ctrl-s, and
ctrl-d. The table below gives a short description.
Step 4 On the command prompt, type “man –S 1 pwd” and press enter. This command will be tackled later in the
course, for now just accept it.
4a. What is the option in the command?
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4b. What is the argument in the command?
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4c. Press “q” to exit the command.
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Step 5 On the command prompt, type “top” and press enter.
5a. Press the control and “c” key at the same time. What happened? Did it have the same effect as pressing “q”?
Why”
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Step 6 On the command prompt, type ”man chmod” and press enter.
6a. Press the spacebar. Did the screen scroll up?
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6b. Press the control and “s” key at the same time and then press the spacebar. Did the screen scroll up? Why?
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6c. This time press the control and “q” key at the same time. What happened?
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6d. What does the command “ctrl-s” and “ctrl-q” do?
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1.4. Changing Password
One of the first things you must do on your user account is to change your password. Password ensures that no one
will have unauthorized access to your user account. A user must have to be authenticated using a password before
access to server will be given. To change your password, use the command: passwd.
You will be prompted by the server of your old password and then will be prompted to input a new password. You will
have to re-type your new password for verification. You can change your password anytime. Password must have at
least six characters with any alphanumeric combination (at least for Linux) but is case sensitive.
Step 7 At the command prompt, type “passwd”.
7a. Enter your current password when prompted for the old password.
7b. Enter the password “h3ll0”, when prompted for the new password.
7c. Was the password rejected? Why was it rejected?
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7d. Enter the password “r3ch3tt” when prompted for the new password.
7e. Was the password was accepted? Why was it accepted?
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7f. What is the message when the password was successfully changed?
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Step 8 At the command prompt, type “passwd“ again. Type the current password as “R4ch3tt”.
8a. Was the password rejected? Why was it rejected?
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8b. What is the message when the password was not successfully changed?
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Step 9 At the command prompt, type “passwd“ again. Enter the current password. Use your desired password when
prompted for a new password. Remember your new password.
9a. Were you able to give a new password on your first try? What were the messages from the server?
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1.5. Basic File Management
Unix file system, like other file systems of other operating systems, consists of files and each file has a file name.
There are three kinds of files on your Unix system: ordinary, special and directories.
The Unix file system is organized as a hierarchy of directories where each directory can contain files or subdirectories.
This hierarchy is called a tree where the root (/) is the top of the tree.
Each file in a directory has a file identifier (this is not synonymous to file name), which is a sequence of characters that
uniquely identifies a file or directory. A file identifier can have at most 255 characters (this includes extension); any
printable character can be used as to name a file but cannot contain “/”. Although the characters “*”, “?”, “>”, “>” or “|”,
it is not recommended because it has special meaning. Remember that filenames in Unix are case sensitive.
File names in Unix, contains a sequence of file identifiers that designates a file. Slashes “/” are used to separate the
sequence of file identifiers. There are two kinds of file name: absolute and relative file name. Absolute file name
specifies the sequence of directories starting from the root (it actually starts with a “/”) and can be used to refer to a file
anywhere in the tree. Relative file name’s starting point is the current directory or working directory. Relative file name
can use symbols “.” and “..” which represents the current directory and parent directory respectively. Another symbol
“~”, represents the home directory. Home directory is the personal directory of a user where your files can be stored.
In order to do basic file management, there are several basic commands that can be used. Usual commands needed
are to list files in a directory, change to another directory, create a new directory, move a file or directory, copy a file or
directory, and remove a file or directory. Most of the commands can use absolute or relative filenames. The commands
are presented in a table below.
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1.5.1. Changing to different directories
The “cd” command is used to change the working directory. Every time you log in via Telnet, you will be in your home
directory. Most of the time, your directory is located in the “/home” parent directory. The hierarchy can be shown as:
The hierarchy shown is very simple. This is not the whole hierarchy for the Unix system. Also, not all hierarchy is the
same for all Unix versions.
Step 10 While you are in the home directory, type the command “pwd”.
10a. What was the message on the screen?
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10b. What does the “pwd” command do?
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Step 11 Type the command “cd /etc” and press enter.
11a. Did the prompt display differently? Write down the display.
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11b. Type the command “pwd”. What is your current working directory?
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Step 12 From the “/etc” directory, type the command “cd /home/<username>”.
12a. Did you go to your “home” directory? How were you able to determine?
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12b. What was the file name used (absolute or relative file name)? Why?
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12c. On the command prompt, type “cd ../../etc” and press enter. Were you able to go to the “/etc” directory?
What was the file name used (absolute or relative file name)? Why?
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12d. From the “/etc” directory, type the command “cd ~”. Were you able to go to the “home” directory? Which “cd”
command is this similar to?
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1.5.2. Listing Directories
The “ls” command is used to list directories. There are a lot of options you can do with the command. It is able to
display all files, directories only and other more options.
Step 13 On the command prompt, type the command “cd ..” and press enter.
13a. Enter the “ls” command. What did you see?
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13b. Enter the “ls -A” command. What is the option? Was it different from last time?
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13c. Enter the “ls -a” command. What is the option? Was it different from last time? What does it do?
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The “ls” command with option “A”, shows all files in the directory including hidden files. Hidden files are files that
start with “.”. The “a” option has the same function as “A” option except that it also displays the “.” (current) and “..”
(parent) directories.
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13d. Enter the “ls -l” command. What is the option? Was it different from last time? What does it do?
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The first column on the “ls -l” shows the file permission of the file or directory (again, will be discussed later).
Notice that a “d” as the first character shows which are the directories.
13e. Enter “cd /etc” and then the “ls -d rc0.d” command. What is the option? What does it do? Is it different from the “ls
rc0.d” command?
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The “d” displays if the “rc0.d” directory is there or not. While the “ls” command without the “d” option will display
the contents of the directory “rc0.d”.
13f. Enter the “ls -R” command. What is the option? What does it do? How is it different from “ls”.
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The “R” option displays the directories recursively.
Step 14 Metacharacters are characters with special meaning in Unix. One of the metacharacters is “*”.
14a. Go to the “/home/dir1” directory, type the command “ls f*”. What files were listed?
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14b. Enter the command “ls p*”. What files were listed?
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14c. Enter the command “ls file?”. What files were listed?
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14d. What is the difference between the commands “ls f*” and “ls file?”?
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14e. Enter the command “ls [f..p]ile1”. What files were listed?
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14f. Enter the command “ls [f..p]ile2”. What files were listed?
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14g. Enter the command “ls [f..p]ile?”. What files were listed?
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14h. What does the metacharacter “[..]” do?
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The metacharacter “*” is a wildcard for multiple characters while “?” is wildcard for a single character. The
metacharacter “[..]” is used to specify a range of characters.
1.5.3. Creating Directories
Directories in the Unix operating system can be created using the “mkdir” command. Naming directories has the same
rules as naming files. Exercises on filenames will be tackled later.
Step 15 Go to your home directory by entering the command “cd ~”. Then create a directory “coffees” using the
command “mkdir coffees”.
15a. Was the directory created?
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15b. Enter the command “cd coffees” and press enter. Next, enter the command “mkdir beans/robusta”. Were
you able to create the directory?
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15c. Enter the command “mkdir -p beans/robusta”. Were you able to create the directory? Why do you think so?
What is the “p” option for?
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The “p” option allows creation of directories with its parent directory.
1.5.4. Filenames
Empty files are files with a size of zero bytes. The “touch” command can be used to create empty files. The “touch”
command will be used to practice creating files with different filenames.
In Unix, filenames can have up to 255 printable characters except for the “/” character. Although “*” and “?” can be
used, these characters have special meaning.
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Step 16 While in the directory “coffees/beans/robusta”, enter the command “touch robusta.txt”.
16a. Were you able to create the file? What is the size of the file? How were you able to determine the file size?
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16b. Enter the command “touch robusta/txt“. Were you able to create the file? Why? What was the message?
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16c. Enter the command “touch robusta1“. Were you able to create the file? Why?
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16d. Enter the command “mkdir robusta.doc“. Were you able to create the directory? Why?
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16e. Enter the command “ls“. Can you tell which one is a directory? What command should be used to be able to
determine which one is a directory?
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16f. Enter the command “ls robusta*“. Is there a difference from the earlier command? Can you tell which one is
the directory? Why?
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1.5.5. Copying Files
The cp command is used to copy files. The command can be used to copy one source to a destination or multiple
sources to a directory.
Step 17 Enter the command “cp robusta.txt robusta.html”.
17a. What happened after entering the command? Did you see the file “robusta.html”?
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17b. Enter the command “cp robusta.txt robusta.doc”. What happened after entering the command? Did you
see the file “robusta.doc“? Why?
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17c. Enter the command “cp robusta.txt robusta.html”. Were you prompted if the file was to be overwritten?
Why?
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17d. Enter the command “cp –i robusta.txt robusta.html”. Were you prompted if the file was to be
overwritten? Why?
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1.5.6. Moving Files
In the Unix operating system, moving of files can be done by using the command “mv”. The command can also be
used to rename files.
Step 18 Enter the command “mkdir -p ../arabica” and press enter. Next, enter the command “touch
arabica.txt”. Use the command “ls” to verify the file is existent.
18a. Enter the command “mv arabica.txt ../arabica”. Is the file “arabica.txt” still there? Where is it located now?
What did the command “mv” do?
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18b. Enter the command “touch arabica.txt” under the directory “<home
directory>/coffees/beans/robusta”. Next, type the command “mv arabica.txt ../arabica”. What happened?
Were you prompted that you will be overwriting a file?
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18c. Enter the command “touch arabica.txt” under the directory “<home
directory>/coffees/beans/robusta”. Next, type the command “mv –i arabica.txt ../arabica”. What
happened? Were you prompted that you will be overwriting a file?
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Answer no to the prompt.
18d. Enter the command “mv arabica.txt arabica.doc”. What happened? Is the file still there? Why?
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The command can be used to rename files.
18e. What is the difference between the command “cp arabica.txt ../arabica” and “mv arabica.txt
../arabica”. Explain.
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1.5.7. Removing Files
Removing or deleting files can be accomplished by using the command “rm”. Be careful in using this command since
deleted file are unrecoverable.
Step 19 Go to the “<home directory>/coffees/beans/robusta” directory. Type the command “rm arabica.doc”.
19a. Was the file still there? Can it be found in another directory? Why?
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Step 20 Enter the command “rm *”.
20a. What happened? Which file or directory was retained?
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20b. Why was it retained?
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Step 21 Go to the “robusta.doc” directory. Create the following directory “bean_quality” and
“bean_quality/perfect_cup”.
21a. Go to the “<home directory>/coffees/beans/robusta”. Enter the command “rm robusta.doc”. Were you
able to remove the directory? Why?
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21b. Enter the command “rm -r robusta.doc”. Were you able to remove the directory? Why? What is the option “r” for?
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Step 22 Go to the “arabica” directory. Enter the command “rm –i arabica.txt”.
22a. Was the file erased immediately? What was the message?
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22b. Answer “y” to the prompt. Was the file removed? What is the option “i” for?
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22c. Go to the “<home directory>/coffees” directory and enter the command
“rm -ir robusta.doc”. Were prompted before removal? What was the message?
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Answer “n” to the prompt.
1.6. Logging Out
The “exit” command can be used to log out of the Unix server.
Step 23 At the prompt type the command “exit”.
23a. What happened? Were you able to log out? Is there an alternative command? (You may research this on books
or in the Internet)
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Name: __________________________________ Date: _____________
Utilities, Redirection and Pipes
2.0 Unix / Linux Command Line Interface (CLI) Basics – Utilities, Redirection and Pipes, vi Text Editor and
Advanced File Commands
The Unix system provides a lot of utilities that one can use. Aside from utilities, the Unix system also provides facilities
for redirection, pipes and file ownership, and file permissions. The Unix system also has a built-in editor called vi.
Although vi may look ugly, vi is the standard text editor you can find in any Unix version and at the same time has
useful features at your fingertips. No need to use the mouse. The objectives of this section are:
1. To familiarize the student in using Unix file and disk utilities.
2. To familiarize the student in using the vi text editor.
3. To familiarize the student on file links.
4. To familiarize the student on file ownership and permissions.
2.1. Utilities
2.1.1. On-line Help
The Unix environment provides a simple on-line help system. The command “man” is used to browse the help pages.
This help system is sometimes referred to as “man pages”. Typing “man ls” at the command prompt will show you
something like:
The man page most of the time will contain the following sections (different Unix versions or authors of man pages
sometimes add sections): name, synopsis, description, and see also. The name section shows the name of the
command and alternative commands that does the same thing. The synopsis section shows the syntax of the
command while the description gives a short text on what the command does and the options that can be used. The
see also section gives other related commands.
Man pages also provide help on programming libraries, utilities, file formats and other topics on the Unix environment.
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Step 1 On the command prompt, type the command “man ls”.
1a. What does the command do?
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1b. Press the spacebar key. What does it do?
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1c. Press the “f” key. What does it do? Is it the same as the space bar key?
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1d. Press the “b” key. What does it do?
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1e. Type the following “/format”. What does it do?
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1f. Press the “q” key. What does it do?
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Step 2 On the command prompt, type the command “man ls”. Scroll the pages and check the sections of the
man page.
2a. Can you identify the sections mentioned? What are these sections?
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2b. Write down the description of the “ls” command.
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2c. Write down an alternative command that you can use to view a help file on ls.
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Step 3 On the command prompt, type the command “man -k dns”.
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3b. What is the “k” option for?
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The “k” option is for searching man pages given a keyword. The argument in the command is the keyword.
In this case, the command looks for man pages that have the word “dns” in it. As a bit information, dns
stands for “Domain Name Server”. Domain name server is a service that allows mapping of Internet names into its IP
address (There will be a section for DNS, please do not worry about it yet. ).
Step 4 On the command prompt, type the command “man -S1 chmod”.
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If you look carefully at the upper right corner of the man page, there is a “( )” after the command. This
indicates in what section of the command are you viewing. Using the “s” option allows you to specify which
section would you want to view. The man utility displays the lowest numbered section by default when no
section number is provided from the command.
2.1.2. The “file” and “wc” Commands
The “file” command allows the user to determine the file type. This is useful if you cannot remember what the file is
for. The “wc” command prints the number of line, words and bytes in a file.
Step 5 At the command prompt, enter the command “cp /home/files/rfc2186.txt rfc2186.txt” and the
command
“cp /home/files/rf2186.pdf rf2186.pdf”.
After copying the files, verify if the files were copied.
5a. At the command prompt, enter the command “file rfc2186.txt”. What type of file is it?
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5b. At the command prompt, enter the command “file NETOPSY_Lab_Manual.pdf”. What type of file is it?
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5c. At the command prompt, enter the command “mv rfc2186.txt rfc2186”. After renaming the file, enter
the command “file rfc2186”. Was it still able to determine the file type?
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Step 6 At the command prompt, enter the command “wc rfc2186”.
6a. What was the output?
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6b. How many bytes, words and lines does the file have?
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6c. At the command prompt, enter the command “wc -c rfc2186”. How many bytes does the file have? Is it
the same as its file size?
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6d. At command prompt, enter the command “wc NETSOPY_Lab_Manual.pdf”. How many bytes, words and
lines does the file have?
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2.1.3. The “more” and “cat” Commands
The “cat” command can concatenate files and print on standard output (which is usually the screen). This is useful
for checking the contents of short file, especially script files (again, will be tackled later). The command can accept
more than one filenames as an argument that can be printed on the standard output.
The problem with the “cat” command is that if the file is too long, the displaying of the file will just flash by. An
alternative command is the “more” command. This command displays the file on the standard output and provides
scrolling capability. Commands for scrolling are the same in the “man” utility.
Step 7 At the command prompt, enter the command “cp /home/files/fruits fruits” and press enter.
After copying the file, enter the command “cp /home/files/vegetables vegetables” and press
enter. Verify if you have copied the file using the “ls” command.
7a. After verifying the files were copied, enter the command “cat fruits”. What did the command do?
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7b. Enter the command “cat vegetables”. What did the command do?
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7c. Enter the command “cat fruits vegetables”. What did the command do?
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7d. Enter the command “cat vegetables fruits”. What did the command do? Is it different from the
previous command? What can you generalize?
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7e. Enter the command “cp /home/files/rfc2186.txt rfc2186.txt”. Verify if the file was copied
using the “ls” command.
7f. Enter the command “cat rfc2186.txt”. What did the command do? Were you able to see anything?
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Step 8 At the command prompt, enter the command “more rfc2186” and press enter.
8a. Are you able to view the file?
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8b. Press the spacebar key. What does it do?
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8c. Press the “f” key. What does it do? Is it the same as the space bar key?
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8d. Press the “b” key. What does it do?
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8e. Press the “q” key. What does it do?
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There are still other commands to scroll the screen in the “more” command. Use the man pages for the
“more” command to check the scroll commands and other options.
2.1.4. The “head” and “tail” Commands
The “head” command outputs the first few lines of a few on the screen while the “tail” command outputs the last few
lines of a file on the screen. The default number of line output is ten (10). These commands useful for checking log
files, especially to network administrators.
Step 9 At the command prompt, type the command “head rfc2186”.
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9b. At the command prompt, type the command “head -c20 rfc2186”. What was the output?
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9c. At the command prompt, type the command “head -n20 rfc2186”. What was the output? How was it
different from last time?
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9d. At the command prompt, type the command “tail rfc2186”. What was the output?
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9e. At the command prompt, type the command “tail -c20 rfc2186”. What was the output?
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9f. At the command prompt, type the command “tail -n20 rfc2186”. What was the output? How was it
different from last time?
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9g. What is the difference between options “c” and “n”?
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2.1.5. The “grep” Command
The “grep” command searches prints the lines in a file with a matching pattern. This is useful for searching patterns
in a text or binary file. Most of the time, network administrators uses this to search if a certain process is running (to
be discussed later) or searching for keywords in a configuration file (again, to e discussed later).
Step 10 At the command prompt, enter the command “grep apple fruits”.
10a. What was the output? Why?
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10b. At the command prompt, enter the command “grep broccoli fruits”. Was there an output? Why?
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10c. At the command prompt, enter the command “grep broccoli vegetables”. Was there an output?
Why?
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2.1.6. The “sort” Command
The “sort” command allows a user to sort alphanumeric text in a file. If the text file has columns, the “sort” command
is able to sort by column. This is useful if you have a spreadsheet like text file.
Step 11 At the prompt, enter the command “cat fruits”. Observe the output of the command.
_________________________________________________________________________
____________________________________________________________________________________________
11b. At the prompt, enter the command “sort fruits”. Observe the output of the command. What was the
output?
_________________________________________________________________________
____________________________________________________________________________________________
Step 12 At the prompt, enter the command “cp /home/files/fruits2 fruits2”.
12a. After copying the file, enter the command “cat fruits2”. Observe the output of the command. What was
the output?
_________________________________________________________________________
____________________________________________________________________________________________
20

12b. At the prompt, enter the command “sort fruits2”. Observe the output of the command. What was the
output?
_________________________________________________________________________
____________________________________________________________________________________________
12c. At the prompt, enter the command “sort -r fruits2”. Observe the output of the command. What was
the output? How is different from the previous command?
_________________________________________________________________________
____________________________________________________________________________________________
12d. At the prompt, enter the command “sort -k1 fruits2”. Observe the output of the command. What was
the output? How is it different from the command in step 2b?
_________________________________________________________________________
____________________________________________________________________________________________
12e. At the prompt, enter the command “sort -r -k1 fruits2”. Observe the output of the command. What
was the output? How is it different from the command in the previous step?
_________________________________________________________________________
____________________________________________________________________________________________
2.2. Redirection and Pipes
Redirectors “redirect” the standard output of a command to a file or device file. This is useful for saving a long list of
directories and files in text file for example. A redirection command looks like:
command > file or command > file_device
The “>” is the redirection symbol. Redirection symbols are:
Pipes are the same as redirection but use the output of a command as input to another command. The pipe symbol is
“|”.
Step 13 At the command prompt, enter the command “ls -l > list”.
13a. Was the text file list created?
_________________________________________________________________________
____________________________________________________________________________________________
13b. Use the “cat” or “more” command to view the “list” text file. What does the text file contain?
_________________________________________________________________________
____________________________________________________________________________________________
21

13c. At the command prompt, enter the command “ls -l > list”. Was a new text file list created? What
does the text file contain? Was it the same as before?
_________________________________________________________________________
____________________________________________________________________________________________
13d. At the command prompt, enter the command “ls -l >> list”. Was a new text file list created? What
does the text file contain? Was it the same as before?
_________________________________________________________________________
____________________________________________________________________________________________
13e. What is the difference between the “>“ and the “>>” redirection symbol?
_________________________________________________________________________
____________________________________________________________________________________________
Step 14 At the command prompt, enter the command “cd /etc/”. After changing to the “/etc” directory, enter the
command “ls -l”.
14a. Were you able to see all the file names? Did just scrolled by?
_________________________________________________________________________
____________________________________________________________________________________________
14b. At the command prompt, enter the command “ls -l |more”. Were you able to see the directory listing
properly?
_________________________________________________________________________
____________________________________________________________________________________________
14c. Which are the commands in the previous command? Which is the pipe symbol?
_________________________________________________________________________
____________________________________________________________________________________________
Remember that the “more” in the command is neither an option nor an argument. “more” is a command
utility that is used to view a file.
Step 15 At the prompt, enter the command “cd ~” and “mkdir dir1 dir2”.
15a. At the prompt, enter the command “ls -l”. Observe the output. What was the output of the command?
_________________________________________________________________________
____________________________________________________________________________________________
15b. At the prompt, enter the command “ls -l |sort -k1”. Observe the output. How is different from the
previous command?
_________________________________________________________________________
____________________________________________________________________________________________
22

15c. At the prompt, enter the command “ls -l |sort -r -k1”. Observe the output. How is different from
the previous command?
_________________________________________________________________________
____________________________________________________________________________________________
15d. At the prompt, enter the command “ls -l |sort -k8”. Observe the output. How is different from the
command in step 3b?
_________________________________________________________________________
____________________________________________________________________________________________
15e. At the prompt, enter the command “ls -l |sort -r -k8”. Observe the output. How is different from
the previous command?
_________________________________________________________________________
____________________________________________________________________________________________
Remember that the “sort” in the command is neither an option nor an argument. “sort” is a command
utility that is used to sort text in a file.
2.3. The vi Text Editor
The vi text editor is a built-in in the Unix operating system. This text editor is a standard on all Unix versions. Most
people would say that vi is not user-friendly, which is very true but vi very powerful. Only the most basic command set
will be tackled in this section. If you need or want to learn more, you can use the man page for vi for further reference
or the suggested reference books in this course.
Vi has three modes of operation: command, entry mode and last-line mode. In the command mode, accepts
command for cursor positioning, going into other modes, deleting characters or lines and searching for string patterns.
The entry mode allows editing of text while the last-line mode allows saving and exiting from vi. Upon starting of vi,
the program goes into the command mode. The following is a summary of the commands:
23

Step 16 At the command prompt, enter the command “vi rfc2186”.
16a. In which mode are in right now?
_________________________________________________________________________
____________________________________________________________________________________________
16b. In the command mode of vi, type “:22”. In which line of test are you in now? (Write down the first few
words of the line)
_________________________________________________________________________
____________________________________________________________________________________________
16c. Go to the word “describes”. Use the cursor keys or (h, j, k, l). Type the “a” command. In which mode are
you in now?
_________________________________________________________________________
____________________________________________________________________________________________
16d. Type the word “cat” and press the escape key. Where did the cursor allowed you to enter text? Before or
after the cursor? In which mode are you in now?
_________________________________________________________________________
____________________________________________________________________________________________
16e. Type the “i” command. In which mode are you in now?
_________________________________________________________________________
____________________________________________________________________________________________
16f. Type the word “hello” and press the escape key. Where did the cursor allowed you to enter text? Before or
after the cursor? In which mode are you in now?
_________________________________________________________________________
____________________________________________________________________________________________
16g. Press the escape the key. In which mode are you in now?
_________________________________________________________________________
____________________________________________________________________________________________
16h. Type the command “x”. What happened? What does the command do?
_________________________________________________________________________
____________________________________________________________________________________________
16i. Type the command “2dd”. What happened? What does the command do?
_________________________________________________________________________
____________________________________________________________________________________________
24

16j. Type the command “yy”. What happened? What did the command do?
_________________________________________________________________________
____________________________________________________________________________________________
16k. Type the “p”. What happened? What did the command do?
_________________________________________________________________________
____________________________________________________________________________________________
16l. Type the command “:wq”. What happened? What did the command do?
_________________________________________________________________________
____________________________________________________________________________________________
16m. Enter the command “vi rfc2186”. Go to line 21. Did vi saved your edited file?
_________________________________________________________________________
____________________________________________________________________________________________
16n. Type the command “yy”. What happened? What did the command do?
_________________________________________________________________________
____________________________________________________________________________________________
16o. Type the “p”. What happened? What did the command do?
_________________________________________________________________________
____________________________________________________________________________________________
16p. Type the command “:q!”. What happened? What did the command do?
_________________________________________________________________________
____________________________________________________________________________________________
16q. Enter the command “vi rfc2186”. Go to line 21. Did vi saved your edited file?
_________________________________________________________________________
____________________________________________________________________________________________
There are other text editors in the Unix system. There is the Emacs text editor and pico. Emacs is
standard in the Unix system while pico is not. The pico text editor is only found in the Linux version of Unix.
You may refer to man pages for pico and Emacs or the suggested references in this course.
25

2.4. Advanced File Commands
2.4.1. Disk Usage and Disk Free
The Unix environment allows the user to check his disk usage and the available disk space in the file system. The
commands are “du” and “df” respectively.
The “du” command allows a user to his/her disk usage including usage in subdirectories. By default, the disk usage is
presented in 1024 bytes per block. If a user sees that his/her disk usage is 108 blocks, this means that it is really
110592 bytes total (108*1024 bytes per block).
The “df” command shows the disk statistics of a file system. Typing “df” on the command prompt will produce an
output on the screen:
Looking at the sample output above, the filesystem column shows the partition/s on the server. The next column,
1kblocks, shows the capacity (total size) of the partition. The Used column shows how much is already used on the
partition, while Available shows how much can still be used. The Use% shows how much percentage is used on the
partition. The Mounted on column shows what is the directory name of the partition.
In the example above, partition /dev/sda2 shows that it has a capacity of around 3.6Gbyte. On the same partition,
around 359Mbyte is already used with still 3.1Gbyte available. Data on the partition occupies only 11% of the disk
space. This partition is mounted as the root (the meaning of mounted will be discussed later in the course). Before
starting the exercise, delete all files in your home directory by entering the command “rm *”.
Step 17 At the command prompt, type the command “cp /home/files/rfc2186.txt rfc2186.txt” and
press enter. This command should be done at your home directory. After the copying the file, type the
command “du” at the command prompt. Observe the numbers.
17a. How many directories do you have? How many blocks are you using in your directory?
_________________________________________________________________________
____________________________________________________________________________________________
17b. At the command prompt, type the command “du -k”. The switch used in the command defines that each
block is 1024 bytes. How many bytes are you using in your home directory?
_________________________________________________________________________
____________________________________________________________________________________________
17c. At the command prompt, type the command “du -ck”. How is this different from the previous command?
_________________________________________________________________________
____________________________________________________________________________________________
Step 18 At the command prompt, type the command “cp /home/files/OPERSYS_Lab_Manual.pdf
OPERSYS_Lab_Manual.pdf” and press enter.
18a. Type the command “du -ck” on the command prompt and press enter. Did the total number of blocks used
increase?
_________________________________________________________________________
____________________________________________________________________________________________
26

18b. How many bytes are you using?
_________________________________________________________________________
____________________________________________________________________________________________
Step 19 At the command prompt, type the command “df”.
19a. How many bytes is one block in the command?
_________________________________________________________________________
____________________________________________________________________________________________
19b. How many bytes is the capacity of /dev/sda1?
_________________________________________________________________________
____________________________________________________________________________________________
19c. How many bytes are used on /dev/sda1?
_________________________________________________________________________
____________________________________________________________________________________________
19d. How many bytes are available on /dev/sda1?
_________________________________________________________________________
____________________________________________________________________________________________
19e. What is the percentage of data used in /dev/sda1?
_________________________________________________________________________
____________________________________________________________________________________________
19f. At the command prompt type the command “df -m”. What is the size of each block in this command?
_________________________________________________________________________
____________________________________________________________________________________________
2.4.2. Hard Links and Soft Links
A file link is a directory entry for a file. Each file has a file name entry with a corresponding information entry that
allows access to the file. A file can have two types of links: hard link and soft link (also sometimes called symbolic
link). A hard link creates a new file name entry for a file but does not create another copy of the file (this is
synonymous to having two pointers point to a file) while a symbolic link creates a new file entry pointing to the original
file entry. Most of the time, symbolic links are more useful since you can use it to create “short cuts” to a directory.
Step 20 At the command prompt, type the command “du -ck”.
20a. What is your total disk usage?
_________________________________________________________________________
____________________________________________________________________________________________
27

20b. At the command prompt, type the command “cp rfc2186.txt rfc_2186.txt”. This will create a copy
the text file “rfc2186.txt”. Verify of the file was created using the “ls -l” command. Was the file
created?
_________________________________________________________________________
____________________________________________________________________________________________
20c. At the command prompt, type the command “du -ck”. What is your total disk usage? Did your disk usage
increased? Why?
_________________________________________________________________________
____________________________________________________________________________________________
20d. View the contents file “rfc2186.txt” by typing the command “more rfc2186.txt”, to exit type “q”.
Also view the contents of the file “rfc_2186.txt” using the command “more rfc_2186.txt”, to exit type
“q”. Were you able to view both files?
_________________________________________________________________________
____________________________________________________________________________________________
20e. Delete the file “rfc_2186.txt” and check your disk usage using the command “du -ck”. What is your
disk usage?
_________________________________________________________________________
____________________________________________________________________________________________
20f. At the command prompt, type the command “ln rfc2186.txt rfc_2186.txt”. This command creates
a hard link for the file “rfc2186.txt” text file. Verify if the hard link was created using the command “ls -
l”. Was the hard link created?
_________________________________________________________________________
____________________________________________________________________________________________
20g. At the command prompt, type the command “du -ck”. What is your total disk usage? Did your disk usage
increased? Why?
_________________________________________________________________________
____________________________________________________________________________________________
20h. View the contents file “rfc2186.txt” by typing the command “more rfc2186.txt”, to exit type “q”. Also
view the contents of the file “rfc_2186.txt” using the command “more rfc_2186.txt”, to exit type “q”.
Were you able to view both files?
_________________________________________________________________________
____________________________________________________________________________________________
28

20i. Delete the file “rfc2186.txt” and try to view the file “rfc_2186.txt” using the more command. Were you
still able to view the file? Why do you think so?
_________________________________________________________________________
____________________________________________________________________________________________
20j. Delete the file “rfc_2186.txt” and copy the file “rfc2186.txt” using the command “cp
/home/files/rfc2186.txt rfc2186.txt”. Verify if the file was copied using the “ls -l” command.
_________________________________________________________________________
____________________________________________________________________________________________
20k. At the command prompt, type the command “ln -s rfc2186.txt rfc_2186.txt”. This command
creates a soft link (symbolic link) for the file “rfc2186.txt” text file. Verify if the hard link was created
using the command “ls -l”. Was the soft link created? How would you know if it were a soft link (do not
use the color of the text to know the difference)?
_________________________________________________________________________
____________________________________________________________________________________________
20l. View the contents file “rfc2186.txt” by typing the command “more rfc2186.txt”, to exit type “q”.
Also view the contents of the file “rfc_2186.txt” using the command “more rfc_2186.txt”, to exit type
“q”. Were you able to view both files?
_________________________________________________________________________
____________________________________________________________________________________________
20m. Delete the file “rfc2186.txt” and try to view the file “rfc_2186.txt” using the more command. Were
you still able to view the file? Why do you think so?
_________________________________________________________________________
____________________________________________________________________________________________
Delete the soft link created for the file “rfc2186.txt”.
Step 21 At the command prompt, type the command “ln -s /home/dir1 test_dir”.
21a. Was the soft link for the directory created?
_________________________________________________________________________
____________________________________________________________________________________________
21b. How do you know if it is a soft link by using the “ls -l” command?
_________________________________________________________________________
____________________________________________________________________________________________
Step 22 On the command prompt type the command “ls /home/dir1” and then type the command “ls
test_dir”.
22a. Were the contents of the directories the same? Why?
_________________________________________________________________________
____________________________________________________________________________________________
29

22b. Use the command “rmdir test_dir” to delete “test_dir”. Were you successful? What was the
message on the screen?
_________________________________________________________________________
____________________________________________________________________________________________
22c. Use the command “rm test_dir” to delete “test_dir”. Were you successful?
_________________________________________________________________________
____________________________________________________________________________________________
2.4.3. File Ownership, File Permissions and Groups
Each file in the Unix system has an owner and permission. Each file is associated to an owner using its user ID. The
username is just a way for us to remember than just a bunch of numbers. A group is a logical grouping of users.
Each group name in the Unix system has a group ID. A group may also have ownership of a file. Most of the time,
the owner has access to the file and modifies the permission of a file.
File permission is way to provide file security in the Unix system. When you enter the command “ls –l”, notice the first
column. The first column in the output of the command shows the file permission of a file. The column is composed
of 10 characters. The first character indicates whether the file is a directory, the next nine characters show the
permission of the file that can be grouped into three columns where each column is composed of three characters.
Each three-character column shows the file permission for the owner, group, and world. Each character in the column
indicates a read, write or execute permission.
The third column in the output of the “ls –l” command shows the owner of the file, while the next column shows which
group can have access to the file or which groups the user belongs to. File permissions are also applicable to
directories.
File permissions can be changed using the “chmod” command. The command uses integers to change the
permission of a file. The command “chmod” is used in the form:
chmod vyz [file_name]
Where vyz is the permission integer to be put into the file. The v is actually a binary representation for rwx. Which “r”
is read, “w” is write and “x” is executable. If a “r” is a logic 1, then the file has read permission, if the “r” is logic 0 then
the file has no read permission. The same rule applies to w and x. For y and z, the rwx rule applies. Example:
chmod 744 rfc2186.txt
This command sets the file permission of the text file “rfc2186.txt” as read, write and executable for owner, read for
group and last, read for world.
Step 23 At the command prompt, enter the command “cp /home/files/rfc2186.txt rfc2186.txt”.
23a. What is the file permission of the owner for the file “rfc2186.txt”? Who is the owner? Which group does
it belong to? What is the group’s file permission?
_________________________________________________________________________
____________________________________________________________________________________________
23b. Enter the command “chmod 444 rfc2186.txt”. Use the vi text editor and try to edit and save the file.
Were you successful? Why?
_________________________________________________________________________
____________________________________________________________________________________________
30

23c. Enter the command “chmod 644 rfc2186.txt”. Use the vi text editor and try to edit and save the file.
Were you successful? Why?
_________________________________________________________________________
____________________________________________________________________________________________
23d. Enter the command “cp /home/files/long_list long_list”. View the file using vi text editor, more
or cat command. What does the file contain? Is it a command? What is the file permission for the owner?
_________________________________________________________________________
____________________________________________________________________________________________
23e. Enter the command “./long_list” at the prompt. What happened? What was the message?
_________________________________________________________________________
____________________________________________________________________________________________
23f. Enter the command “chmod 766 long_list” at the prompt. What is the file permission for the owner
after the command was executed?
_________________________________________________________________________
____________________________________________________________________________________________
23g. Enter the command “./long_list” at the prompt. What happened? What is the command similar to?
_________________________________________________________________________
____________________________________________________________________________________________
Step 24 At the prompt, enter the command “ls -ld /home/student_files”.
24a. Who is the owner of the file? What is the file permission of the owner? Which group does the directory
belong to? What is the group permission? What is the world permission?
_________________________________________________________________________
____________________________________________________________________________________________
24b. At the prompt, enter the command “groups”. To which group do you belong?
_________________________________________________________________________
____________________________________________________________________________________________
24c. At the prompt, enter the command “cd /home/student_files”. In the directory, enter the command
“touch <username>”. Were you successful? Why?
_________________________________________________________________________
____________________________________________________________________________________________
24d. At the prompt, enter the command “cd /home” and also enter the command “ls -ld faculty_files”.
Who is the owner of the file? What is the file permission of the owner? Which group does the directory
belong to? What is the group permission? What is the world permission?
_________________________________________________________________________
____________________________________________________________________________________________
31

24e. At the prompt, enter the command “cd /home/faculty_files”. In the directory, enter the command
“touch <username>”. Were you successful? Why?
_________________________________________________________________________
____________________________________________________________________________________________
32

Name: __________________________________ Date: _____________
Processes, Unix Shells, and Shell Scripts
3.0 Unix / Linux Command Line Interface (CLI) Basics – Processes, Unix Shells and Shell Scripts
The Unix system allows job control because each command or program executed in the Unix system is a considered
a process. Job control allows running of processes, killing processes or creating background processes. The “ps”
command shows which processes are running on the system. This like the “ls” command for processes. Running
processes can also be terminated using the “kill” command. Job control will be discussed more in the course.
The Unix shell is a program that allows interactive use of the Unix operating system and the computer hardware.
There are different shells created for the Unix system. The first shell was the Bourne shell. After the Bourne shell,
the Korn and C shell was later created. The Korn shell is a superset of the Bourne shell while the C shell was “C” like
(“C” as in the C programming language). Although there are several shells available, the shells have the same set of
features with only subtle differences. For example, the “history” command is not available in the Bourne shell but is
available in the Korn and C shells. The prompts of different shells also look different.
Today, the Linux system uses the Bourne Again shell. This “new” shell has the useful features of Korn and C shells.
You could say that it is the hybrid of the Korn and C shell. Do remember that the Bourne Again shell is only in Linux
versions of Unix systems.
As mentioned earlier, these shells have same set features. These features are aliasing, environment setting,
variables and shell programming or also known as shell scripts. These features will be discussed in better detail in
this section.
Shell scripts allow a user to make useful utilities using Unix commands or other utilities. Shell scripts also have
constructs like programming languages that allow flexibility.
With a minimum background of shells, scripts and job control, the objectives of this section are:
1. Familiarization with Unix shells, it features and how to use it.
2. Familiarization with Unix shell scripts and how create and use shell scripts.
3. Familiarization with controlling jobs on the Unix system.
3.1. Processes
One of the ability of the Unix system is run several programs at a time. This is called multi-tasking. The Unix system
is the first system to provide this feature. Each process running on the Unix system has a process ID. Since there are
several programs running at the same time, there must be a way to control these programs or processes. There are
several types of processes on the Unix system. Two basic types of processes is the parent and child process. As the
name implies, the parent spawns a child process. If the parent process terminates before the child process returns, the
child process will become an orphan. If the child process does not return, it is a zombie or defunct process. Also, the
“daemon” process has the process ID of 1 which is the “main” parent of the processes in the Unix system.
Users can control the process using the “ps” and “kill” command; that allow a user to control processes. When the
“ps” command is executed, the following will be seen on the screen.
The first column shows the process id. The second column shows which terminal is running it while the third column
shows how much processing time is being used by the process. Fourth column shows the name or the command
name.
33

The “kill” command can be used to terminate a process. When the “kill” command is used, make sure you know
the process ID. There are two ways to kill a process, soft kill and hard kill. With the soft kill, processes are terminated
properly while the hard kill terminates a process abruptly.
Step 25 On the prompt, type the command “ps”.
25a. How many processes are running? Are the processes running only yours?
_________________________________________________________________________
____________________________________________________________________________________________
25b. On the prompt type the command “ps -e”. Are all the processes displayed yours? If not, some of the
processes belong to whom?
_________________________________________________________________________
____________________________________________________________________________________________
25c. On the prompt type the command “ps -f”. Is the number or columns different from last time? What is the
“f” option for?
_________________________________________________________________________
____________________________________________________________________________________________
25d. On the prompt type the command “ps -e |more”. What does the command do?
_________________________________________________________________________
____________________________________________________________________________________________
25e. On the prompt type the command “ps -e |grep min”. What does the command do?
_________________________________________________________________________
____________________________________________________________________________________________
Step 26 On the prompt enter the command “sleep 1000” and open another remote session to same server. Do
not exit your first remote session.
26a. Using the new remote session, at the prompt, enter the command “ps -u <user name>”. Were you able
to see the “sleep” program? What is the process ID of the “sleep” program?
_________________________________________________________________________
____________________________________________________________________________________________
26b. At the prompt, kill the “sleep” program using the “kill <pid>” command. Was the “sleep” program
terminated?
_________________________________________________________________________
____________________________________________________________________________________________
26c. Log-out of the new remote session. If ever the process cannot be killed using the soft kill command, use
the command “kill -9 <pid>” (hard kill). Before using the command, use the soft kill first because it
terminates a process properly than the hard kill command.
Step 27 At the prompt, enter the command “sleep 1000 &”.
34

27a. Was this command different from last time? Why?
_________________________________________________________________________
____________________________________________________________________________________________
The “&” at the end of the command tells the shell to make it a background process.
27b. At the prompt, enter the command “ps -f”. Looking at the “PPID” column, what is the parent ID of the
process of the “sleep” process? Why was it the parent?
_________________________________________________________________________
____________________________________________________________________________________________
27c. Kill the sleep program.
Step 28 At the prompt, enter the command “ps -f”. Record the process ID of the current shell.
28a. At the prompt, open a new shell using the command “bash” and then enter the command “sleep 1000
&”. Use the command “ps -f” to check the processes. What is the parent ID of the “sleep” program?
_________________________________________________________________________
____________________________________________________________________________________________
28b. Exit the new shell by using the command “exit”. Enter the command “ps -f”. What is the parent id of
the “sleep” process? Which is this process? Why did it changed?
_________________________________________________________________________
____________________________________________________________________________________________
Since the process that spawned the sleep program was terminated before the sleep program ended, the
sleep program is now called an orphan. Notice that the daemon process adopted the sleep program.
28c. Kill the “sleep” process that was orphaned. Were you able to kill it?
_________________________________________________________________________
____________________________________________________________________________________________
3.2. The Unix Shell
As mentioned earlier, the shell allows an interactive use of the Unix system and the computer hardware. Without it, it
will be hard to use the Unix system and computer. There are different shells available in the Unix system. These
shells have same set of features with only little differences. Most of the time, their differences are how the commands
are entered.
3.2.1. Bourne Shell (bsh), Bourne Again Shell (bash) and C Shell (csh or tcsh)
The Bourne, Bourne Again and C shell are different shell available on the Linux version of the Unix system. These
three shells have differences that are only minor. The Bourne and C shell were already available on all Unix system
and were the original shells. When Linux came, the Bourne Again shell was developed by the Free Software
Foundation. The Bourne Again shell incorporates useful features of the Korn and C shells.
Step 29 On the prompt, enter the command “csh”. Observe what happens to the prompt. Always take note that
you are in the C shell.
35

29a. What is does your prompt your look like? Why do you think the prompt changed? (In this case, the usual
prompt for the C shell in most Unix systems is “%” but in Linux, it has different prompt.)
_________________________________________________________________________
____________________________________________________________________________________________
29b. On the prompt, enter the following commands: “ls -l”, “ls”. Try using the up and down cursor keys.
Were you able to call the previous commands? Why do you think so?
_________________________________________________________________________
____________________________________________________________________________________________
29c. Clear the command prompt and type the command “history”. What was the output?
_________________________________________________________________________
____________________________________________________________________________________________
29d. On the prompt, type the command “!!”. What does the command do?
_________________________________________________________________________
____________________________________________________________________________________________
29e. On the prompt, type the command “vi this_is_a_file_with_a_long_name.txt”. Type in the text
“The quick brown fox jumps over the lazy dog.” Save the text file. Try to display the file using the “cat this_”
then press the “tab” key. What happened? Did the shell complete the filename? Why do you think so?
_________________________________________________________________________
____________________________________________________________________________________________
Step 30 Type the command “exit” at the command prompt and enter the command “bsh”.
30a. Did the prompt changed? What does the prompt look like?
_________________________________________________________________________
____________________________________________________________________________________________
30b. On the prompt, enter the following commands: “ls -l”, “ls”. Try using the up and down cursor keys.
_________________________________________________________________________
____________________________________________________________________________________________
30c. On the prompt, type the command “history”. What was the output?
_________________________________________________________________________
____________________________________________________________________________________________
30d. On the prompt, type the command “cat this_“ then press the “tab” key. What happened? Did the shell
complete the filename? Why do you think so?
_________________________________________________________________________
____________________________________________________________________________________________
36

Step 31 Type the command “exit” at the command prompt.
31a. On the prompt, enter the following commands: “ls -l”, “ls”. Try using the up and down cursor keys.
_________________________________________________________________________
____________________________________________________________________________________________
31b. Clear the command prompt, and then enter the command “history”. What happened?
_________________________________________________________________________
____________________________________________________________________________________________
31c. On the prompt, type the command “touch testfile” and then enter the command “vi !*”. What
happened? What does the command do?
_________________________________________________________________________
____________________________________________________________________________________________
31d. On the prompt, type the command “cat this_” then press the “tab” key. What happened? Did the shell
complete the filename? Why do you think so?
_________________________________________________________________________
____________________________________________________________________________________________
3.2.2. Shell Features
“alias” Command
An alias allows a way to give a different name or shorter name for a command. This allows a user to “personalize”
some commands that are used often.
Step 32 On the prompt, enter the command “alias ll=“ls-l“”. Again on the prompt, enter the command “ll”.
32a. What is the output of the command? What is the equivalent of the command?
_________________________________________________________________________
____________________________________________________________________________________________
32b. What other command can you think of that you might need an alias? (Include the options for the command)
_________________________________________________________________________
____________________________________________________________________________________________
32c. On the prompt, type the command “unalias ll”. Enter the command “ll” at the prompt. What
happened? Where you able to show the listing of you directory? Why not?
_________________________________________________________________________
____________________________________________________________________________________________
32d. What does the alias and “unalias“ command do?
_________________________________________________________________________
____________________________________________________________________________________________
37

“set” Command
The set command allows setting and unsetting of flags that control shell-wide characteristics. There are a lot flags
available on the Unix system. What will be presented are the useful ones.
Step 33 At the prompt, enter the command “ls > list” and then enter the command “cat list”.
33a. At the prompt, enter the command “ls -l > list” and then enter the command “cat list”. Was the
text file overwritten? Why?
_________________________________________________________________________
____________________________________________________________________________________________
33b. At the prompt, enter the command “set -o noclobber” and then enter the command “ls > list”.
Were you allowed to overwrite the file? What does the command do?
_________________________________________________________________________
____________________________________________________________________________________________
33c. At the prompt, enter the command “set +o noclobber” and then enter the command “ls > list”.
Were you allowed to overwrite the file? What does the command do?
_________________________________________________________________________
____________________________________________________________________________________________
Step 34 At the prompt, enter the command “set -o verbose” and then enter the command “ls -l”.
_________________________________________________________________________
____________________________________________________________________________________________
34b. At the prompt, enter the command “set +o verbose” and then enter the command “ls -l”. Did it
turned off the verbose mode? Why?
_________________________________________________________________________
____________________________________________________________________________________________
Command Sequencing
Several commands can be executed in succession in the Unix system. By using the “;”, commands can be sequenced
together. The Unix system is also able to do conditional sequencing. With conditional sequencing, a command will only
be executed if the first one is successful or the next command will only be a executed if there was an error.
Step 35 At the prompt, type the command “date; ls -l |more”.
35a. What did the command do? Did it execute two commands in succession?
_________________________________________________________________________
____________________________________________________________________________________________
35b. At the command prompt, type the command “date; ls; pwd > out.txt”. View the text file using a
text editor or “cat” command. What was on the “out.txt” file? (Describe)
_________________________________________________________________________
____________________________________________________________________________________________
38

35c. At the command prompt, type the command “(date; ls; pwd) > out.txt”. View the text file using a
text editor or “cat” command. What was on the “out.txt” file? (Describe)
_________________________________________________________________________
____________________________________________________________________________________________
35d. Why were the output of the two previous command were different? What was the command?
_________________________________________________________________________
____________________________________________________________________________________________
Step 36 At the prompt, type the command “mkdir dir1” then enter the command “ls -d dir1 && echo
”Directory found” Notice that this is a conditional command. The “&&” specifies that the next
command will be executed when the first command is successful.
36a. Did it execute the second command?
_________________________________________________________________________
____________________________________________________________________________________________
36b. At the prompt, type the command “ls -ld dir3 && echo “Directory found“”. Did it execute the
second command? Why?
_________________________________________________________________________
____________________________________________________________________________________________
Shell Variables
Shell variables are store information required by processes so that processes can function properly. An example of a
variable is how your command prompt looks like. The variable is called PS1. There are two types of shell variables:
local and global (also known as environment variable). Local variables are variables that are available for the current
shell session only while global variables are variables that are available to the current and all child or sub-shells that
the user or the system might start
Step 37 At the prompt, enter the command “my_name=“<your first name>“” and then enter the command
“echo $my_name”.
37a. What was the output of the command? Were you able to create a variable?
_________________________________________________________________________
____________________________________________________________________________________________
37b. At the prompt, enter the command “echo my_name”. Was the output same as before? Is the “$” sign
needed to display the value of the variable? Why?
_________________________________________________________________________
____________________________________________________________________________________________
37c. What did you create? A local or global variable?
_________________________________________________________________________
____________________________________________________________________________________________
39

37d. At the prompt, enter the command “bsh” and then enter the command “echo $my_name”. Were you able
to see you name?
_________________________________________________________________________
____________________________________________________________________________________________
37e. Without exiting the shell yet, type the command “my_name=“<your first name> <your last
name>“” and enter the command “echo $my_name”. Were you able to see your name? Explain why you
were not able to see your name earlier?
_________________________________________________________________________
____________________________________________________________________________________________
37f. Exit the shell and enter the command “echo $my_name”. Was the output same as previous shell? Why?
_________________________________________________________________________
____________________________________________________________________________________________
37g. At the prompt, enter the command “export my_name” and then enter the command “bsh”. Display the
variable “$my_name” by using the command “echo $my_name”. Is the output the same with the previous
shell? Why?
_________________________________________________________________________
____________________________________________________________________________________________
37h. What did you create? Local or global variable?
_________________________________________________________________________
____________________________________________________________________________________________
Step 38 At the command prompt, enter the command “PS1=”%”.
38a. What happened to the prompt? Did it changed?
_________________________________________________________________________
____________________________________________________________________________________________
Notice that PS1 is a shell variable. It was created by the operating system. In this case, the variable PS1
holds the text or command what the prompt should look like.
38b. At the prompt, enter the command “set |more”. What did it displayed? Were able to find PS1?
_________________________________________________________________________
____________________________________________________________________________________________
38c. At the command prompt, enter the command “PS1=”[u@h W]$” ”. Did the command prompt
go back to original state?
_________________________________________________________________________
____________________________________________________________________________________________
40

There are special characters that the shell can accept for the prompt setting. These settings are:
38d. Using the command “set |more”, find the shell variable for your log-in name. Is there shell variable for it?
What is the name of the variable?
_________________________________________________________________________
____________________________________________________________________________________________
38e. Using the command “set |more”, find the shell variable for your home directory. Is there shell variable for
it? What is the name of the variable?
_________________________________________________________________________
____________________________________________________________________________________________
Initialization Files
Initialization files or scripts can contain series of commands, settings and variables. Initialization files allows a user to
personalize some settings. There are two types of initialization files: system wide and personal. The system wide
initialization is set by the administrator and is the default initialization file. The personal initialization file resides in the
user’s home directory and can be “personalized” by the user. In the bash shell, there are two initialization files, the
“.bash_profile” and the “.bashrc”. The first initialization file can contain shell variable settings while the second
initialization file contains alias settings. The “.bash_profile” can also contain other command that can be executed
during the logging in.
Step 39 At the prompt, enter the command “PS1=%”. Make sure that the prompt has changed and enter the “exit”
command.
39a. Login to the server and check the prompt. Were you able to change the prompt? Did it go back to its
original state?
_________________________________________________________________________
____________________________________________________________________________________________
39b. Edit the “.bash_profile” using the vi text editor. At the end of the file, enter the text “PS1=“[u@h
W]$“”. Save the text file and exit. Login to the server again and check the prompt. Did the prompt
changed permanently?
_________________________________________________________________________
____________________________________________________________________________________________
Step 40 At the prompt, enter the command “alias ll=“ls “l“”. Enter the command “ll”.
40a. Were you able to see the effect of the alias?
_________________________________________________________________________
____________________________________________________________________________________________
41

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