Tutorial2: Unix / Linux File Management

UNIX / LINUX FILE MANAGEMENT CONCEPTS

Main Objectives of this Practice Tutorial

• Understand the purpose of directories and directory pathnames.

• Use common Unix / Linux commands to perform directory management tasks.

• Use Text Editors to create and modify text files

• Use Common Unix / Linux commands to manage and manipulate text files.

Tutorial Reference Material

Course Notes	Linux Command/Shortcut Reference		YouTube Videos
Slides: PDF | PPTX Tutorials: Nano Reference Sheet (PDF) Vi Reference Sheet (PDF) Les Czegel's Week 2 Notes (HTML)	File Management pwd cd ls tree mkdir rmdir cp mv rm , rm -r	Text Editors / File Content vi , *nano cat more , less head , tail touch file find diff sort uniq grep	Brauer Instructional Videos: Basic File Actions (touch, ls -l, cp, cp -r, mv, mkdir, mkdir -p, rm, rmdir, rm -r)

KEY CONCEPTS

Unix / Linux Directories

In Unix / Linux (as opposed to MS Windows), there are no drive letters (such as C:, or D:).

All files and directories appear under a single ancestor directory called "the root directory".

To better organize files (eg. text, images, documents, spreadsheets, programs) within your Matrix account, they should be stored in directories. To further organize many files, directories
may contain sub-directories.

The Unix/Linux file system is hierarchical, like other operating systems such as Windows, Mac OSX, etc. In Unix / Linux (as opposed to MS Windows), there are no drive letters (such as C:, or D:).
All files and directories appear under a single ancestor directory called the "root directory".

Learning how to issue Linux commands for navigating and manipulating directory and files within the the Linux filesystem are essential skills for Linux users and Linux system administrators (i.e. sysadmins).

In the Linux (Unix) OS, the "root directory" / is the starting directory, and other "child directories", "grandchild directories", etc. can be created as required. The hierarchical structure resembles an "upside-down tree". There is actually a command called tree that displays a "directory tree diagram"!

Directory Pathnames

A pathname points to a file system location by following the directory tree hierarchy.

A pathname is used to specify a route to a file within the file system.

A pathname points to a file system location by following the directory tree hierarchy expressed in a string of characters in which path components, separated by a delimiting character, represent each directory. The delimiting character is most commonly the slash ("/"). Reference: https://en.wikipedia.org/wiki/Path_(computing)

The following table displays and defines commonly used directories
(listed by directory pathname) for for ALL Unix / Linux Filesystems:

Common directory pathnames
for for ALL Unix / Linux Filesystems.

Directory Pathname	Purpose
/	Root directory (ancestor to all directories)
/home	Used to store users’ home directories
/home/username	A specific User's Home Directory
/bin	Common system binaries (commands)
/usr/bin	Common utilities (commands) for users.
/usr/sbin	Common utilities for system administration
/etc	System administration files (eg. passwd)
/var	Dynamic files (log and mail files)
/tmp , /var/tmp	Temporary files for programs
/dev	Device driver files (terminals, printers, etc.)

When you log into your Matrix account, you are automatically directed to your home directory.
This directory is where the user can store files, and create subdirectories to organize their files.

INVESTIGATION 1: CREATING & MANAGING DIRECTORIES

In this investigation, you will learn how to create, navigate, list directory contents and remove directories in your Matrix account.

Directory File Naming Rules

Before you learn how to create directories, it is important to understand what represents an appropriate directory filename.

Listed below are some common file-naming rules:

• Unix/Linux characters are case sensitive. It is recommended to be consistent (e.g. use all lowercase letters)
• Adopt a consistent directory naming scheme (this will help you to navigate within your directory structure)
• Make your directory names meaningful
• Avoid non-alphanumeric characters, as they may have a special meaning to the system that will make your work more difficult when changing to directories, etc.
• Avoid using spaces for directory names (consider periods, hyphens, and underscores instead)

Part 1: Creating Directories

Tree Diagram of Directory Structure to Create in your Home Directory (displayed in blue text).

Creating subdirectories within your home directory makes it more efficient to
save and access files on your Linux server.

A comparison would be rooms in a house. If there were no rooms, just one large room in a 3,000 square foot house, it would be "messy" and difficult to locate items. Each room in a house is used to for a
specific purpose to be more productive to perform a task such as a kitchen, bedroom, bathroom, etc.

You will be creating the following directory structure within your home directory
(refer to diagram on the right side).

Perform the Following Steps:

NOTE: For several of the following commands, you will be using your Seneca username to replace the text:"your-seneca-id" in a pathname.

For example, if your Seneca user ID was mkhan then you would display
the pathname /home/your-seneca-id as: /home/mkhan

1. Login to your matrix account (you should know how to do this from performing Tutorial 1 INVESTIGATION 1]).
   
   
2. Issue a command to confirm that you are located in your home directory
   (you should know how to do this from performing [Tutorial 1 INVESTIGATION 2]
   
   
3. Issue the following Linux command: mkdir /home/your-seneca-id/uli101xx
   (remember: use your Seneca username instead of "your-seneca-id")
   
   NOTE: You should always confirm that you have created a directory.
   This can be done by issuing the ls command.
   
   
   

   Creating and Confirming the Creation of a Directory.
4. Issue the following Linux command: ls /home/your-seneca-id/uli101xx
   
   There are no contents that are contained in this newly-created directory; therefore, no contents appear. A useful option -d can be used to confirm that the actual directory has been created as opposed to viewing the contents of the directory.
   
   
5. Issue the following Linux command: ls -d /home/your-seneca-id/uli101xx
   
   You should now see just the directory listed. You can also combine the -d and -l options to provide more detail regarding the newly-created directory.
   
   
6. Issue the following Linux command: ls -d -l /home/your-seneca-id/uli101xx
   
   How can you confirm from the output of this command that the file uli101xx is a directory?
   
   
7. Issue the following Linux command: ls -ld /home/your-seneca-id/uli101xx
   
   Is the output from this command the same was the output from the previous command?
   If so, what does this say about how to use multiple options for Linux commands?
   
   
8. Issue the following Linux command to create the acp100xx and xyz100xx directories:
   mkdir /home/your-seneca-id/acp100xx /home/your-seneca-id/xyz100xx
   
   NOTE: You can create multiple directories by issuing the mkdir command with multiple arguments.
   
   
9. Issue the following Linux command to confirm that those directories have been created:
   ls -ld /home/your-seneca-id/acp100xx /home/your-seneca-id/xyz100xx
   
   Using a FULL pathname starting from the root directory (i.e. /) requires is a LOT of typing!.
   Since we are already located in our home directory, we don't have to start from
   the root directory called a "relative" pathname.
   
   
10. We will now create the subdirectories that are contained in the uli101xx directory.
    Issue the following Linux command to move to the uli101xx directory using a relative pathname:
    cd uli101xx
    
    
11. Issue a Linux command to confirm that your current location is in the uli101xx directory.
    You should know how to issue this command from a previous tutorial.
    
    
12. Issue the following Linux command to create the directories called notes, tutorials and examples:
    mkdir notes tutorials examples
    
    
13. Issue a Linux command to confirm that those directories have been created
    (you should already know how to do this).
    
    There are better ways to create the same directory structure without using the cd command.
    
    Issuing the cd command prior to issuing other commands indicates to others that you are a novice or "newbie".
    You can actually lose marks on quizzes or examples if you issue multiple Linux commands to performed tasks that can be performed
    using a single Linux command with pathnames.
    
    
14. Issue the following Linux command to return to your home directory: cd
    
    
15. Issue a Linux command to confirm that you are now located in your home directory.
    
    Although we will teach you how to remove directories and their contents in another section,
    let's remove the created directory structure' and recreate the same directory structure
    using just one command using pathnames.
    
    
16. Issue the following Linux command to remove all of the directories that you have created:
    rm -r uli101xx acp100xx xyz100xx
    
    
17. Issue a Linux command to confirm that the uli101xx, acp100xx and xyz100xx that been removed.
    
    
18. Issue the following single Linux command to create the entire directory structure:
    mkdir -p uli101xx/notes uli101xx/tutorials uli101xx/examples acp100xx xyz100xx
    
    NOTE: The -p option allows "parent" directories to be automatically created first to then create their subdirectories.
    
    
19. Issue the following Linux command to confirm that all of the directories have been created:
    ls -ld uli101xx/ uli101xx/notes uli101xx/tutorials uli101xx/examples acp100xx xyz100xx

Running a Shell Script to Check your Work

Although you are being asked to create the directory structure, you might have made some mistakes:
For Example:

• Forgetting to create a directory.
• Making syntax errors (eg. spelling or mixing up character case)
• Not creating subdirectories within specified directories.

If all all check pass, then user performed task correctly and can continue.

If there is a warning, then feedback is provided to user to correct and re-run checking script.

To check for mistakes, a shell script has been created to check your work. If the checking shell script detects an error, then it will provide feedback and offer constructive feedback on how to fix that problem so you can re-run the checking shell scripts until your work is correct.

Perform the Following Steps:

1. Make certain that your current directory is your home directory.
   
   
2. Issue the following Linux command to run a checking script:
   bash /home/murray.saul/scripts/week2-check-1
   
   
3. If you encounter errors, then view the feedback to make corrections, and then re-run the checking script. If you receive a congratulation message that there are no errors, then proceed to the next section.

Part 2: Viewing Directory Contents / Copying & Moving Directories

Now that you have learned how to efficiently create your directory structure, you will now learn how to issue Linux commands
to view directory contents as well as copy and move directories.

Perform the Following Steps:

Output of the tree command to display directory structure.

Output of the ls -R command to display directory structure.

1. Issue the following Linux command: tree
   
   NOTE: You should see the directory structure that you created in the previous section. You can also issue the tree command using a directory pathname to display the directory structure for a specific scope.
   
   You can also use the -R option for the ls command to display all directories and subdirectories for a specified directory path (referred to as a recursive directory listing).
   
   
2. Issue the following Linux command: ls -lR
   
   What directories do you see?
   
   
3. Issue the following Linux command: ls -lR uli101xxx
   
   Note the differences between both of these commands (i.e. using and not using a pathname).
   
   You can copy and move entire directories (and their contents) to other directories.
   
   

   Output of the tree command to confirm copy of uli101xx directory (and contents) to the xyz100xx directory.

   Output of the tree command to confirm movement of acp100 directory directory (and contents) to the xyz100xx diredtory.

4. Issue the following Linux command:
   cp -R uli101xx xyz100xx
   
   
5. Issue the following Linux command to display the directory structure of your home directory to confirm you copied the uli101xx directory:
   tree
   
   
6. Issue the following Linux command:
   mv acp100xx xyz100xx/uli101xx/tutorials
   
   
7. Issue the following Linux command to display the directory structure of your home directory to confirm you moved the acp100xx directory:
   tree
   
   Let's run a checking script to see if you moved and copied the directories correctly.
   
   
8. Make certain that your current directory is your home directory.
   
   
9. Issue the following Linux command run checking script:
   bash /home/murray.saul/scripts/week2-check-2
   
   
10. If you encounter errors and re-run the checking script until you receive a congratulations message, and proceed to the next section.
    
    

Part 3: Removing Directories

In this section, we will learn how to safely remove directories and their contents.

Perform the Following Steps:

1. Confirm that you are located in your home directory.
   
   The rmdir command is used to remove empty directories.
   
   
2. Issue the following Linux command to remove the empty directory called tutorials: rmdir uli101xx/tutorials
   
   
3. Issue a command to confirm that you removed the tutorials directory.
   
   
4. Issue the following Linux command to remove the empty directory called uli101xx: rmdir uli101xx
   
   NOTE: You should get an error message, since the uli101xx directory is NOT empty.
   
   To remove non-empty directories, you can use the rm -r command.
   The -r option stands for recursive, which can travel down the directory paths and their contents.
   
   
5. Issue the following Linux command to remove the uli101xx directory and its contents: rm -r uli101xx
   
   
6. Issue the tree command to confirm that the uli101xx directory (contained in your home directory) and its contents have been removed.
   
   NOTE: To safely remove non-empty directories, you can add the -i option which will prompt the user if they wish to remove contents as it your travel recursively down a directory to remove directories and their contents.
   
   
7. Issue the following Linux command (entering "y" when prompted): rm -ri xyz100xx
   
   NOTE: You should have removed all directories that you have created.
   
   Let's run a checking script to confirm that you have correctly removed all of those directories.
   
   
8. Issue the tree command to confirm that all of those recently created directories have been removed.
   
   
9. Issue the following Linux command to run a checking script to confirm removal of those directories:
   bash /home/murray.saul/scripts/week2-check-3
   
   
10. If you encounter errors and re-run the checking script until you receive a congratulations message, and proceed to the next INVESTIGATION.
    
    

INVESTIGATION 2: MANAGING TEXT FILES

The Nano Text Editor is Easy to Operate for Novice Users.

The vi Text Editor, although taking longer to master, has outstanding features and allow the user to be more productive with editing text files.

Since IT students will be working in the Unix / Linux command line environment, it is useful to learn a least two common command-line text editors.

Although programming students can use graphical IDE's to code and compile programs, they can create source code using a text editor and compile their source code in the Matrix server to generate executable programs (without having to transfer them for compilation or execution).

Networking and Tech Support students can use a text editor to edit configuration files. These students in upper grades will become familiar with the process of installing, configuring, and running network services and text editors are an important tools
to help setup but also "tweak" or make periodic changes in networking services configuration.

The two most readily-available command line text editors in Linux are Nano and vi.
The Nano text editor would seem like an easier-to-use text editor, but vi (although taking longer to learn)
has outstanding features and allow the user to be more productive with editing text files.

Part 1: Creating Text Files Using The Nano Text Editor

You will now learn basic editing skills using the Nano text editor including creating, editing, and saving text files.

Perform the Following Steps:

1. Make certain that you are located in your home directory.
   
   
   
2. Create the following directory structure (displayed on the right side) by issuing a single Linux command
   (You should know how to do this from the previous INVESTIGATION).
   
   
3. Issue a Linux command to check that you correctly created those directories.
   
   
4. Issue the following Linux command to edit a text file called mytext.txt in the linux/practice directory:
   nano textedit/practice/mytext.txt
   
   NOTE: When using the Nano text editor, you are placed in INPUT mode, so you can enter text immediately.
   
   
   

   Enter the following text that appears in this diagram.
5. Enter the lines shown in the other diagram of the nano text editor on the right side.
   
   NOTE: Refer to the table below for a list of
   common Nano navigation & editing commands:
   
   

   Key(s)	Purpose
   <ctrl><SPACEBAR>	Move forward one word
   <esc><SPACEBAR>	Move back one word
   <ctrl><k>	Cut line
   <esc>^	Copy Line (Note: to get ^ character, type <shift>6, not <ctrl>)
   <ctrl><u>	Paste Cut/Copied Text
   <ctrl><g>	Display help screen (ctrl-x to exit help screen)

   
   
6. Referring to the table above, practice navigating and editing your entered lines for practice.
   
   
7. To save your editing session, press: <ctrl>x
   
   
8. You will be prompted to modify your file: type the letter y for yes.
   
   
9. The name of the file will be displayed, Press ENTER.to save editing changes for that file name.
   
   NOTE: This prompt for file name allows you to change the name of the file if you wish.
   By pressing ENTER, it will accept the default filename.
   
   
10. Practice editing the file ( using the nano command in step #4 ) and perform more editing operations,
    (just type more random lines at the bottom of this file) and then save your editing session and exit your text editor.
    
    

Part 2: Creating Text Files Using The vi Text Editor

Using the vi text editor.

You will now learn basic editing skills using the vi (vim) text editor including
creating, editing, and saving text files.

The vi (vim) text editor (although taking longer to learn) has outstanding features to increase coding productivity. The major different between nano and vi is that vi starts in COMMAND LINE mode. You need to issue letter commands to perform text editing or press colon “: ” to enter last line mode to issue more complex commands.

Perform the Following Steps:

1. Make certain that you are located in your home directory.
   
   
2. Issue the following Linux command to edit a text file called othertext.txt in the linux/practice directory:
   vi textedit/practice/othertext.txt
   
   NOTE: When using the Nano text editor, you are placed in COMMAND mode,
   so you need to issue a command to switch to INPUT mode.
   
   
   

   Enter the following text that appears in this diagram.
3. Type the following key to enter INPUT mode: i
   
   
4. Enter the line shown in the other diagram of the vi text editor on the right side.
   
   
5. While on the first line, press the following key to enter COMMAND mode: ESC
   
   NOTE: Refer to the table below for a list of
   the most common vi (vim) navigation & editing commands:
   
   

   Key(s)	Purpose
   i	Enter INPUT mode
   <esc>	Return to COMMAND MODE
   x	Delete text to the right in COMMAND mode
   W	Move forward one word in COMMAND mode
   B	Move back one word in COMMAND mode
   dd	Cut line in COMMAND mode
   yy	Copy Line in COMMAND mode
   p / P	Paste Cut/Copied Text below/above line in COMMAND mode
   u	Undo previous editing command
   :help	Display help screen in COMMAND mode
   :x	Save editing changes and exit (in COMMAND mode)
   :w name	Save editing changes to "name" in COMMAND mode
   :q!	Abort editing session and exit (in COMMAND mode)

   
   Once you can get used to working in INPUT and COMMAND mode, it is easier to perform text editing operations in vi in COMMAND mode as opposed to nano!
   
   
6. Type the following keys to copy the current line: yy
   
   
7. Type the following key to copy the current line: p
   
   What did you notice?
   
   
8. Type the following keys: u
   
   What did you notice?
   
   
9. Type the following key to undo changes: u
   
   What did you notice?
   
   
10. Type the following keys: 3p
    
    What did you notice?
    
    
    

    Use a combination of arrow keys and the w and b keys while in COMMAND mode to change the correct words for the third and fourth lines.
11. Use up or down arrow keys to move to the second line.
    
    
12. Type either the w and/or b keys to move the cursor to the beginning of the word: first.
    
    
13. Type the x keys to remove the word called first.
    
    
14. Type the i key to enter INSERT mode.
    
    
15. Type the word: second
    
    
16. Press the ESC key to enter COMMAND mode.
    
    
17. Repeat steps 11 to 16 to change the words for lines 3 and 4.
    
    
18. Move to the 4th line (i.e. last line).
    
    
19. Type the following keys: dd
    
    What did you notice?
    
    Let's save editing changes and exit the vi text editor.
    
    
20. Type the following keys: :x
    
    What did you notice?
    
    
21. Issue the same command that you performed in Step #2 to confirm that you had properly edited that file.
    
    
22. Save and exit your vi editing session.
    
    
    

    The online vi-tutorial provides users "hands-on" experience of using the vi text editor.
    An online tutorial has been created to give you "hands-on" experience on how to use vi text editor. It is recommended that you run this online tutorial in your Matrix account to learn how to create and edit text files with the vi text editor.
    
    
23. Issue the following to run the vi online tutorial:
    /home/murray.saul/vi-tutorial
    
    
24. In the tutorial menu, select the first menu item labelled "USING THE VI TEXT EDITOR"
    
    
25. Read and follow the instructions in the tutorial. Eventually, it will display a simulated vi environment and will receive step-by-step instructions on how to use this text editor.
    
    
26. When you have completed that section, you will be returned to the main menu.
    If you want to get extra practice, you can select the menu item labelled "REVIEW EXERCISE".
    
    
27. When you want to exit the tutorial, select the menu option to exit the tutorial.
    
    

Part 3: Manage / Manipulate Text File Content

We conclude this tutorial by learning to view or manipulate the display file content without having to use a text editor.
This is HIGHLY ADVISED in case you only want to view contents and NOT edit file contents by mistake.

Perform the Following Steps:

1. Refer to the following table of Text File Management commands :
   
   

   Linux Command	Purpose
   touch	Create empty file(s) / Updates Existing File's Date/Time Stamp
   cat	Display text file's contents without editing (small files)
   more , less	Display / Navigate within large text files without editing
   cp	Copy text file(s)
   mv	Move / Rename text files
   rm	Remove text file(s)
   sort	Sorts (rearranges) order of file contents when displayed. Content is sorted alphabetically by default. The -nItalic text option sorts numerically, -r performs a reverse sort
   head , tail	Displays the first / last 10 lines of a text file by default. An option using a value will display the number of lines (e.g. head -5 filename will display first 5 lines, tail -5 filename will display last 5 lines).
   grep	Displays file contents that match a pattern
   uniq	Displays identical consecutive lines only once
   diff file1 file2	Displays differences between 2 files
   file	Gives info about the contents of the file (e.g. file with no extention)
   find	To find files matching specified characteristics:

   
   
2. Confirm that you are located in your home directory.
   
   
3. Use the touch command to create the empty files called a.txt, b.txt, and c.txt
   
   
   

   Nano text editor containing numbers 1 to 40
   on separate lines.
4. Use the nano text editor to edit the empty file called a.txt.
   
   Type the number "1" and press ENTER. On the second line, type the number "2" and press ENTER.
   Continue entering increasing number values until you reach the number 40 on line 40.
   
   
5. Save your editing session.
   
   
6. Issue the following Linux command: cat a.txt
   
   Can you see all of the contents?
   
   
7. Issue the following Linux command: more a.txt
   
   Can you view or at least navigate to see all of the contents?
   What is the advantage of using the more command?
   
   
8. Type the letter "q" to exit the more command.
   
   
9. Issue the following Linux command: less a.txt
   
   Is there any difference between the more and less commands?
   (again press q to quit)
   
   
10. issue the following Linux command: sort a.txt
    
    Why does the output not look what you expected? Why?
    
    
11. Issue the following Linux command: sort -n a.txt
    
    Try the same command using both the -n and -r options to see what happens.
    
    
12. issue the following Linux command: head a.txt
    
    What is the output from this command display?
    
    
13. issue the following Linux command: head -7 a.txt
    
    What is the output from this command display?
    
    
14. issue the following Linux command: tail a.txt
    
    What is the output from this command display?
    How would you issue this command to display only the last line contained in that file?
    
    
15. Issue the following Linux command: grep 2 a.txt
    
    What type of output appear? Why did these lines appear (what do they all have in common)?
    
    
16. Edit the a.txt file and add to the bottom 5 new lines each consisting of the same text: "end of line" and save changes to your file.
    
    
17. Issue the following Linux command: uniq a.txt
    
    What do you notice happened to those newly created lines?
    
    
18. Issue the following Linux command: cp a.txt a.txt.bk
    
    
19. Issue the following Linux command: cp a.txt b.txt
    
    
20. Issue one of the commands you learned to display the contents of the file called b.txt without editing.
    
    What happened to this file?
    
    
21. Issue the following Linux command: mv a.txt aa.txt
    
    
22. Issue a Linux command to view the directory contents.
    
    What happened to the file called a.txt? Why?
    
    
23. Issue the following Linux command: file b.txt
    
    What sort of information did it provide?
    
    
24. Issue the following Linux command: diff aa.txt b.txt
    
    What was the output? Why do you think caused the result of this output?
    
    
25. Issue the following Linux command: diff aa.txt c.txt
    
    What reason would this type of output occur?
    
    
26. Issue the following Linux command: find -P .
    
    What is the output of this command?
    
    
27. Issue the following Linux command:
    rm aa.txt b.txt a.txt.bk c.txt
    
    
28. Issue the ls command to verify that these files have been removed.
    
    
29. After you complete the Review Questions sections to get additional practice, then work on your
    online assignment #1, section 2 "Basic Unix Commands" (parts 4 to 6) labelled:
    Managing Files , Accessing Files and Review Exercise.
    
    

LINUX PRACTICE QUESTIONS

The purpose of this section is to obtain extra practice to help with quizzes, your midterm, and your final exam.

Here is a link to the MS Word Document of ALL of the questions displayed below but with extra room to answer on the document to simulate a quiz:

https://ict.senecacollege.ca/~murray.saul/uli101/uli101_week2_practice.docx

Your instructor may take-up these questions during class. It is up to the student to attend classes in order to obtain the answers to the following questions. Your instructor will NOT provide these answers in any other form (eg. e-mail, etc).

Review Questions:

For each of the following questions, use a pathname starting from the root directory (i.e. “/”).

1. Write a single Linux command to create the directory structure starting from your home directory from the diagram displayed on the right.
2. Write a Linux command to display a detailed listing of history directory.
   How would this command differ if you wanted to also view hidden files as well?
   
3. Write a Linux command to change to the project directory.
   What command would you issue to return to your home directory?
   
4. Write a Linux command to copy the project directory and its contents to the history directory.
5. Write a Linux command to move the directory called directories to the history directory.
6. Write a Linux command to remove both directories named 1 and 2.
7. Write a Linux command to remove the concepts directory and its contents.
8. Write a Linux command to remove the concepts directory and prompt the user if they want to remove this directory’s contents.
   
   
9. Write a single Linux command to create the following empty files in the concepts directory:
   myfile.txt
   yourfile.txt
   thefile.txt
   
10. Write a Linux command to view the contents of the myfile.txt text file to prove it is empty.
    What is the difference between the commands: cat, more and less?
11. Write a Linux command to sort the contents of a file called practice/customers.txt
12. Write a Linux command to display the first 4 lines of a file called practice/customers.txt
13. Write a Linux command to display the last line of a file called practice/customers.txt
14. Write a Linux command to match a line containing the pattern Linux in a file called practice/customers.txt
15. Write a Linux command to display unique occurrences of consecutive lines in a file called practice/customers.txt
16. Create a table listing each Linux command, useful options that are displayed near the top of this tutorial labelled: Tutorial Reference Material