Basic Linux Commands

In this guide, you'll learn essential Linux commands for navigating the file system and managing files and directories. We'll walk through exercises that involve building a directory structure using Linux shell commands.

The top-level directory (/home/Michael) already exists since it is Michael’s home directory. You will create subdirectories inside it manually. In this exercise, we create four continent directories (Asia, Europe, Africa, and America) under /home/Michael. Under each continent, country directories—and for some, city directories—are added. Each bullet point in the description below represents a directory.

When you log in as the user Michael, your starting point is the home directory (/home/Michael). To confirm your current location, run the following command:

pwd

Expected output:

/home/michael

To list the contents of the home directory, use:

ls

If no output is returned, the directory is empty.

Creating Directories

Begin by creating the continent directories. The mkdir (make directory) command can create one or more directories in a single command:

mkdir Asia Europe Africa America

After running this command, use ls to verify that the directories have been created successfully.

Creating Country and City Directories

Next, create the country directories. For example, to add countries in Asia:

1. Change into the Asia directory:

   cd Asia
   

2. Confirm your current directory:

   pwd
   

   Expected output:

   /home/michael/Asia
   

3. Create country directories, such as China and India:

   mkdir China India
   

There are several ways to create a city directory (for instance, Mumbai under India). You can either change into the India directory and then create the city directory:

cd India
mkdir Mumbai

Or, you can create the city directory from within the Asia directory using a relative path:

mkdir India/Mumbai

If the parent directory (India) does not exist and must be created along with the city directory, add the -p option:

mkdir -p India/Mumbai

Navigating the File System

To move up one level (for example, from the Asia directory back to /home/Michael), use:

cd ..

Running cd without arguments will return you to your home directory:

cd

You can also navigate by specifying the entire path:

cd /home/michael

Bob follows the same steps on his laptop to replicate this directory structure in his home directory (/home/Bob).

Absolute vs. Relative Paths

When moving around the file system, you have two options: absolute paths and relative paths. For example, if you're in /home/Michael and want to navigate to the Asia directory:

• Using an absolute path:

  cd /home/Michael/Asia
  

• Using a relative path:

  cd Asia
  

An absolute path begins from the root directory (/) and provides the full location, whereas a relative path is based on your current working directory.

pushd /etc
popd

Modifying the Directory Structure

The exercise also involves modifying the directory layout to meet specific requirements. An earlier error involved creating the "Morocco" directory under Europe instead of Africa. The correct organization places Morocco under Africa. The image below illustrates the comparison between the original and the desired directory structures:

Other required modifications include:

• Fixing a typo in the Mumbai directory name.
• Copying the file city.txt from the Mumbai directory to the Cairo directory.
• Removing the file Tottenham.txt from the London directory.

An additional image confirms these changes:

Moving Directories

To relocate the Morocco directory from Europe to Africa, use the mv command. When using absolute paths:

mv /home/michael/Europe/Morocco /home/michael/Africa/

Or, if you are already in /home/michael, employ relative paths:

mv Europe/Morocco Africa/

Renaming Directories

If the directory name "Mumbai" contains a typo, rename it using the mv command:

mv Asia/India/Mumbai Asia/India/MumbaiCorrected

Replace "MumbaiCorrected" with the intended directory name.

Copying Files

To copy the city.txt file from the Mumbai directory to the Cairo directory (located in Africa/Egypt), use:

cp Asia/India/Mumbai/City.txt Africa/Egypt/Cairo/

Deleting Files

To remove the file Tottenham.txt from the London directory (in Europe), use:

rm Europe/UnitedKingdom/London/Tottenham.txt

Working with Files

Reading File Contents

To display the contents of a file—such as city.txt in the Mumbai directory—use the cat command:

cat Asia/India/Mumbai/City.txt

Expected output:

Mumbai

Writing to Files

To replace the content of a file, like updating the Cairo version of city.txt, use redirection with cat:

cat > Africa/Egypt/Cairo/City.txt

After executing the command, type the new content. Press Ctrl+D when finished to save and exit.

Creating an Empty File

To create an empty file—such as country.txt in the China directory—use the touch command:

touch /home/michael/Asia/China/Country.txt

Viewing Files with Pagers

For a more manageable view of file contents, you can use pagers like more and less.

Using more:

more new_file.txt

Key controls for more:

• Space: scrolls one screen.
• Enter: scrolls one line.
• b: scrolls back one full screen.
• /: begins a text search.
• q: quits the viewer.

Using less offers additional navigation controls:

less new_file.txt

Key controls for less:

• Up Arrow: scrolls up one line.
• Down Arrow: scrolls down one line.
• /: begins a text search.
• q: quits the viewer.

More powerful text editors are available for advanced file manipulation and will be covered in a dedicated section later.

Listing Files

The ls command lists the contents of directories. For a basic listing, use:

ls

For a detailed view showing file permissions, ownership, and timestamps, add the -l option:

ls -l

Example output:

total 0
-rw-rw-r-- 1 bob bob 0 Mar 13 11:30 File.txt
-rw-rw-r-- 1 bob bob 0 Mar 13 11:30 index.html
-rw-rw-r-- 1 bob bob 0 Mar 13 11:30 caleston

To include hidden files (those starting with a dot), use:

ls -a

Example output:

.  ..  File.txt  index.html  caleston  .test

Here, . refers to the current directory and .. to the parent directory.

To sort files by modification time (newest first), use:

ls -lt

For a list from oldest to newest, use:

ls -ltr

This guide covered fundamental Linux commands for effectively navigating and manipulating your file system. With these basics, you can work more efficiently and manage your directories and files with ease.

Additional Resources

• Linux Command Line Basics
• Linux Documentation

Happy learning and exploring Linux!