1. To view what's written in a file.

    [ec2-user@masternode react_django_demo_app]$ ls
    api         docker-compose.yaml  frontend   README.md         tests
    db.sqlite3  Dockerfile           manage.py  requirements.txt  todo_drf
    [ec2-user@masternode react_django_demo_app]$ cat requirements.txt
    asgiref==3.2.3
    Django==3.0.3
    django-cors-headers==3.2.1
    djangorestframework==3.11.0
    pytz==2019.3
    sqlparse==0.3.0
    [ec2-user@masternode react_django_demo_app]$
   

2. To change the access permissions of files.

    [ec2-user@masternode react_django_demo_app]$ ls -al
    total 168
    drwxr-xr-x. 7 root     root       4096 May  3 18:12 .
    drwx------. 5 ec2-user ec2-user    154 May  3 18:59 ..
    drwxr-xr-x. 4 root     root        179 May  3 18:12 api
    -rw-r--r--. 1 root     root     143360 May  3 18:12 db.sqlite3
    -rw-r--r--. 1 root     root         77 May  3 18:12 docker-compose.yaml
    -rw-r--r--. 1 root     root        144 May  3 18:12 Dockerfile
    drwxr-xr-x. 5 root     root        124 May  3 18:12 frontend
    drwxr-xr-x. 8 root     root        163 May  3 18:12 .git
    -rw-r--r--. 1 root     root          4 May  3 18:12 .gitignore
    -rw-r--r--. 1 root     root        628 May  3 18:12 manage.py
    -rw-r--r--. 1 root     root        109 May  3 18:12 README.md
    -rw-r--r--. 1 root     root        113 May  3 18:12 requirements.txt
    drwxr-xr-x. 3 root     root         44 May  3 18:12 tests
    drwxr-xr-x. 3 root     root        108 May  3 18:12 todo_drf
    [ec2-user@masternode react_django_demo_app]$ sudo chmod 777 requirements.txt
    [ec2-user@masternode react_django_demo_app]$ ls -al
    total 168
    drwxr-xr-x. 7 root     root       4096 May  3 18:12 .
    drwx------. 5 ec2-user ec2-user    154 May  3 18:59 ..
    drwxr-xr-x. 4 root     root        179 May  3 18:12 api
    -rw-r--r--. 1 root     root     143360 May  3 18:12 db.sqlite3
    -rw-r--r--. 1 root     root         77 May  3 18:12 docker-compose.yaml
    -rw-r--r--. 1 root     root        144 May  3 18:12 Dockerfile
    drwxr-xr-x. 5 root     root        124 May  3 18:12 frontend
    drwxr-xr-x. 8 root     root        163 May  3 18:12 .git
    -rw-r--r--. 1 root     root          4 May  3 18:12 .gitignore
    -rw-r--r--. 1 root     root        628 May  3 18:12 manage.py
    -rw-r--r--. 1 root     root        109 May  3 18:12 README.md
    -rwxrwxrwx. 1 root     root        113 May  3 18:12 requirements.txt
    drwxr-xr-x. 3 root     root         44 May  3 18:12 tests
    drwxr-xr-x. 3 root     root        108 May  3 18:12 todo_drf
    [ec2-user@masternode react_django_demo_app]$
   

3. To check which commands you have run till now.

    [ec2-user@masternode ~]$ history
        1  whoami
        2  users
        3  useradd master
        4  sudo useradd master
        5  users
        6  cat /etc/passwd
        7  usermod -l master masternode
        8  usermod -l masternode master
        9  sudo usermod -l masternode master
       10  cat /etc/passwd
       11  userdel master
       12  userdel masternode
       13  sudo userdel masternode
       14  ls -ld /home/master/
       15  rm -rf /home/master/
   

4. To remove a directory/ Folder.

    [ec2-user@masternode ~]$ ls
    react_django_demo_app  testdir
    [ec2-user@masternode ~]$ rm -rf testdir/
    [ec2-user@masternode ~]$ ls
    react_django_demo_app
    [ec2-user@masternode ~]$
   

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

    [ec2-user@masternode testdir]$ touch fruits.txt
    [ec2-user@masternode testdir]$ ls
    fruits.txt
    [ec2-user@masternode testdir]$ cat fruits.txt
    [ec2-user@masternode testdir]$
   

6. Add content in devops.txt (One in each line) - Git, GitHub, Jenkins, Maven, Docker, Kubernetes, Linux, Terraform.

    [ec2-user@masternode testdir]$ vi devops.txt
   

   To edit the file click i key to insert and add the content to the file then to save click ESC+ :wq

7. To Show only the top three lines from the file.

    [ec2-user@masternode testdir]$ head -3 devops.txt
    Git
    GitHub
    Jenkins
    [ec2-user@masternode testdir]$
   

8. To Show only bottom three lines from the file.

    [ec2-user@masternode testdir]$ tail -n 3 devops.txt
    Kubernetes
    Linux
    Terraform
    [ec2-user@masternode testdir]$
   

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

    [ec2-user@masternode testdir]$ touch Colors.txt
    [ec2-user@masternode testdir]$ cat Colors.txt
   

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

    [ec2-user@masternode testdir]$ vi Colors.txt
    

    To edit the file click i key to insert and add the content to the file then to save click ESC+ :wq

11. To find the difference between fruits.txt and Colors.txt file.

    [ec2-user@masternode testdir]$ diff devops.txt Colors.txt
    1,8c1,8
    < Git
    < GitHub
    < Jenkins
    < Maven
    < Docker
    < Kubernetes
    < Linux
    < Terraform
    ---
    > Red
    > Pink
    > White
    > Black
    > Blue
    > Orange
    > Purple
    > Grey
    [ec2-user@masternode testdir]$
    

Stay tuned for such content !!

Thank you for reading.