Day 3 Task: Basic Linux Shell Scripting for DevOps Engineers.

Day 3 Task: Basic Linux Shell Scripting for DevOps Engineers.

What is Kernel

The kernel is a computer program that is the core of a computer’s operating system, with complete control over everything in the system.

What is Shell

A shell is a special user program which provides an interface for the user to use operating system services. Shell accepts human-readable commands from a user and converts them into something which the kernel can understand. It is a command language interpreter that executes commands read from input devices such as keyboards or from files. The shell gets started when the user logs in or start the terminal.

What is Linux Shell Scripting?

A shell script is a computer program designed to be run by a Linux shell, a command-line interpreter. The various dialects of shell scripts are considered to be scripting languages. Typical operations performed by shell scripts include file manipulation, program execution, and printing text.


Explain in your own words and examples, what is Shell Scripting for DevOps.

Shell scripting for DevOps is all about 🤖 automating and orchestrating tasks and processes in a DevOps environment using 📜 shell scripts. It involves writing scripts in shell programming languages (such as Bash, PowerShell, or Python) to streamline repetitive tasks, enable process automation, and facilitate the integration and deployment of software. 🚀

What is #!/bin/bash? can we write #!/bin/sh as well?😒

The line "#!/bin/bash" is known as a shebang or hashbang. It is commonly placed at the beginning of a shell script file and specifies the interpreter to be used to execute the script. In this case, "/bin/bash" indicates that the script should be interpreted and executed by the Bash shell.

Bash (Bourne Again Shell) is a popular and feature-rich shell that is commonly used as the default shell on many Linux distributions. It is backwards-compatible with the original Bourne shell (/bin/sh) and provides additional functionality and improvements.

Now, regarding the use of "#!/bin/sh," it specifies the Bourne shell as the interpreter for the script. The Bourne shell is an older shell that lacks some of the advanced features and capabilities found in Bash. However, it is more lightweight and is still available on most Unix-like systems.

  • Write a Shell Script which prints I will complete #90DaysOofDevOps challenge


echo "I will Complete #90DaysOfDevOps Challenge"

First, create a file using touch

Then vi

Press I on the keyboard to insert

Write you content

Press the esc Key on the keyboard

Write :wq press enter to save and quit Vim

Give permission to file the execute using chmod -x

At last type ./

  • Write a Shell Script to take user input, input from arguments and print the variables.

  • Write an Example of If else in Shell Scripting by comparing 2 numbers


# Compare two numbers

if [ $num1 -eq $num2 ]; then
    echo "The numbers are equal."
elif [ $num1 -gt $num2 ]; then
    echo "Number 1 is greater than Number 2."
    echo "Number 2 is greater than Number 1."

Top 100 Linux Commands Cheat Sheet:

  1. cd — Change directory

  2. ls — List directory contents

  3. pwd — Print working directory

  4. cat — Concatenate and display files

  5. touch — Create an empty file

  6. cp — Copy files and directories

  7. mv — Move or rename files and directories

  8. rm — Remove files and directories

  9. mkdir — Create a new directory

  10. rmdir — Remove an empty directory

  11. cut — Cut out sections of a file

  12. gzip — Compress or decompress files using gzip

  13. gunzip — Decompress files compressed with gzip

  14. find — Find files and directories matching a pattern

  15. grep — Search for a pattern in a file

  16. awk — Pattern scanning and processing language

  17. sed — Stream editor for filtering and transforming text

  18. head — Display the first few lines of a file

  19. tail — Display the last few lines of a file

  20. sort — Sort lines of a file

  21. uniq — Remove duplicate lines from a file

  22. wc — Count lines, words, and characters in a file

  23. diff — Compare two files line by line

  24. patch — Apply a patch to a file

  25. chmod — Change permissions of files and directories

  26. chown — Change the owner of a file or directory

  27. chgrp — Change the group ownership of a file or directory

  28. ps — List running processes

  29. top — Display system resource usage and process information

  30. kill — Send a signal to a process to terminate it

  31. du — Display disk usage of files and directories

  32. df — Display free disk space on the file system

  33. mount — Mount a file system

  34. umount — Unmount a file system

  35. ping — Test connectivity to a network host

  36. ssh — Secure shell remote login and command execution

  37. scp — Secure copy files between hosts

  38. rsync — Remote file and directory synchronization

  39. curl — Transfer data from or to a server using various protocols

  40. wget — Retrieve files from the web using various protocols

  41. ftp — File Transfer Protocol client

  42. sftp — Secure File Transfer Protocol client

  43. telnet — Telnet client

  44. nslookup — DNS lookup utility

  45. dig — DNS lookup utility

  46. netstat — Display network connections and statistics

  47. ifconfig — Configure network interfaces

  48. route — Display or modify the routing table

  49. iptables — Firewall and packet filtering utility

  50. hostname — Display or set the hostname of the system

  51. date — Display or set the system date and time

  52. timedatectl — Control the system date and time

  53. uname — Display system information

  54. whoami — Display the current user ID

  55. id — Display user and group information

  56. su — Switch user to become another user

  57. sudo — Execute a command with superuser privileges

  58. passwd — Change the password of a user account

  59. useradd — Create a new user account

  60. userdel — Delete a user account

  61. usermod — Modify a user account

  62. groupadd — Create a new group

  63. groupdel — Delete a group

  64. groupmod — Modify a group

  65. finger — Display information about users on the system

  66. last — Display information about recent logins

  67. history — Display command history

  68. echo — Print a message to the terminal

  69. printf — Format and print data

  70. lshw — Displays hardware information

  71. lspci — Displays information about PCI buses and devices.

  72. lsusb — Displays information about USB buses and devices.

  73. hwinfo — Displays detailed hardware information.

  74. free — Displays memory usage.

  75. vmstat — Displays system memory, processor, and I/O statistics.

  76. iostat — Displays CPU and disk I/O statistics.

  77. uptime — Displays system uptime and load averages.

  78. journalctl — Displays the system journal.

  79. dmesg — Displays the kernel ring buffer.

  80. crontab — Schedules recurring tasks.

  81. at — Schedules a one-time task.

  82. service — Manages system services.

  83. systemctl — Controls system services in systemd-based distributions.

  84. traceroute — Traces the network path to a remote host.

  85. bzip2 — Compresses files using the bzip2 algorithm.

  86. unzip — Extracts files from a ZIP archive.

  87. tee — Redirect output to multiple files

  88. chroot — Change the root directory for a process

  89. ps aux — Display information about all running processes

  90. less — Display file contents in a paginated format

  91. more — Display file contents one page at a time

  92. ln — Create links between files

  93. realpath — Print the resolved absolute path of a file

  94. watch — Execute a command periodically and display the output

  95. cal — Display a calendar

  96. tar -xzvf — Extract files from a compressed archive

  97. tar -czvf — Create a compressed archive

  98. whereis — Locate the binary, source, and manual page files for a command

  99. locate — Find files by name

  100. which — Display the full path to an executable