Diving deeper in basic Linux🏊‍♀️

Diving deeper in basic Linux🏊‍♀️

Day-03 of 90DaysOfDevOps

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Let's directly jump into the commands by doing some tasks that will cover some major Linux basic commands.

1️⃣Task 1

To view what's written in a file🔎

Let's say I have a file called linux-basic.txt and in this text-based file there is some content written on it. And you want to see the contents.

Then there is a command for that called cat

Cat is used to concatenate and display files on the terminal.

  • cat -n: This adds line numbers to all lines

  • cat –E: This shows $ at the end of the line

2️⃣Task 2

To change the access permissions of files🔐

There will be a case where you don't want others to modify your file or vice-versa. To change the permissions of files, there is a command called chmod

chmod 755 linux-basic.txt

This sets the permissions of linux-basic.txt to read, write, and execute for the owner, and read and execute for the group and others.

  • The next three characters, rwx, indicate the permissions for the file owner (ubuntu in this case). It means the owner has read (r), write (w), and execute (x) permissions.

  • The following three characters, r-x, indicate the permissions for the group (ubuntu in this case). It means the group has read and execute permissions but does not have write permission.

  • The last three characters, r-x, represent the permissions for others (users not in the owner or group). They have read and execute permissions but no write permission.

You can manage the accessibility according to you, like above.

3️⃣Task 3

To check which commands you have run till now🗒️

To perform the above task, there is a command called history, where you can see all the commands you have used till now.

4️⃣Task 4

To remove a directory/ Folder📤

To remove a file, there is a command called rm ie remove. But we cannot remove a folder by running just rm cmd. There is another cmd to remove a folder that is called rm -rf

The rm -rf command is a more powerful variation that forcefully removes files and directories recursively without prompting for confirmation.

  • -r (or --recursive): This option enables the removal of directories and their contents recursively.

  • -f (or --force): This option overrides any prompts or warnings and forcefully removes files and directories without asking for confirmation.

5️⃣Task 5

To create a fruits.txt file and to view the content🧺

  1. Create fruits.txt file - To perform this, there are two ways you can consider.

    • Run touch cmd, this will create a file with no content. Then run vi/vim cmd, this will open up a text editor where you can write whatever you want by changing its mode to insert(i) and then esc > :wq! to save and exit from the editor.

    • Or you can run directly vi/vim fruits.txt cmd, this creates a file and open-up the editor directly.

        $vi fruits.txt
      
        This file is created to list my favourite fruit ie MANGO.
        --
        --
        :wq!
      
  2. To view the content of the file - Run cat cmd as we have discussed earlier.

     $ cat fruits.txt
     This file is created to list my favourite fruit ie MANGO.
    

6️⃣Task 6

Add content in devops.txt (One in each line) - Apple, Mango, Banana, Cherry, Kiwi, Orange, Guava🥗

To perform the above task, we have to create a file called devops.txt and then add on some given contents. Let's do that!

Again, there are two ways (some more ways, comments :)

Method 1: Using a text editor

  1. Open the devops.txt file in a text editor (such as Nano or Vim).

  2. Add the fruits manually, each on a new line.

  3. Save the file and exit the text editor.

Methos 2: By using echo cmd

echo -e "Apple\nMango\nBanana\nCherry\nKiwi\nOrange\nGuava" >> devops.txt

This command appends the fruits to the file, with each fruit on a new line.

  1. echo: The echo command is used to display text or values on the terminal.

  2. -e: This option is specific to the echo command and enables the interpretation of backslash escapes. In this case, it allows the interpretation of \n as a newline character.

  3. "Apple\nMango\nBanana\nCherry\nKiwi\nOrange\nGuava": This is the string of text to be echoed. It consists of multiple fruits separated by newline characters (\n), ensuring each fruit is on a new line.

  4. >>: The double greater-than symbol (>>) is a redirection operator in the shell. It appends the output of the command to the specified file instead of displaying it on the terminal.

  5. devops.txt: This is the filename of the file where the output of the echo command will be appended. In this case, it is devops.txt.

7️⃣Task 7

Show only the top three fruits from the file🥭

To perform the above task we have,

head -n 3 devops.txt

This command displays the first three lines (fruits) from the file.

  • head: The head command is used to display the first few lines of a file or input stream. By default, it displays the first 10 lines of a file.

  • -n: The -n option is specific to the head command and is used to specify the number of lines to be displayed.

  • 3: In this case, 3 is the argument provided after the -n option. It specifies that we want to display the first three lines of the file.

8️⃣Task 8

Show only the bottom three fruits from the file🥝

This is similar to the above task-7. Predictable, right?

tail -n 3 devops.txt

This command displays the last three lines (fruits) from the file.

9️⃣Task 9

To create another file Colors.txt and to view the content🧮

This is also what we have done above so I am not explaining this.

$vi Colors.txt

This file is created to list my fav colors ie Yellow & Blue.
--
--
:wq!
$ cat Colors.txt
This file is created to list my fav colors ie Yellow & Blue.

1️⃣0️⃣Task 10

Add content in Colors.txt (One in each line) - Red, Pink, White, Black, Blue, Orange, Purple, Grey🎨

Again, you know this.

echo -e "Red\nPink\nWhite\nBlack\nBlue\nOrange\nPurple\nGrey >> Colors.txt

1️⃣1️⃣Task 11

To find the difference between fruits.txt and Colors.txt files☯️

To perform the above task, there is a command called diff to see the difference between two files.

$diff fruits.txt Colors.txt

  1. To see a side-by-side comparison, use the -y option:

     $diff -y fruits.txt Colors.txt
    
  2. To see a context-based comparison, you use the -c option:

     $diff -c fruits.txt Colors.txt
    
  3. To generate a unified diff, you use the -u option:

     $diff -u fruits.txt Colors.txt
    

Thank you!🖤