Linux Command Line Interface and BASH Scripting

Linux is an open source operating system that enables applications and users to access hardware devices, with code that anyone can modify and customize.

Linux terminal acts as a gateway to manage files, folders, hardware, and software via a command line interface. Automate tasks with simple scripts and use powerful commands for efficiency.

Explore the Linux file system hierarchy rooted at /, with directories like /bin, /boot, /dev, /home, /lib, and /proc. Learn how devices become files and where libraries reside.

Explore the terminal interface by identifying the logged-in user Ibrahim, the machine Ubuntu, and the current directory—the slash home directory.

Discover how to use man and --help to view command options, read help pages in the less viewer, and quickly understand Linux commands in the terminal.

Use pwd to display the current directory and cd to move to the root or other directories, with practical terminal examples.

learn how the ls command lists files and directories in a directory, with an example in the root partition, and note that many options exist to customize listings.

Explore the dash l option for the ls command, revealing detailed file information such as permissions, owner, size, and date in a directory.

Learn how the ls -lh option displays file sizes in a human readable format, converting bytes to megabytes and kilobytes, and how to combine options as -l -h or -lh.

Explore how ls -lhS lists files with details in human readable format, ordered by size from largest to smallest, and note how option order can affect results for some commands.

Explore the ls command options -a and -A to reveal all files, including hidden ones, and learn how dot files (.) and the parent directory (..) affect listings.

Learn to navigate the Linux file system by using ls and cd together, differentiating between logical and absolute paths, and moving from root to home to documents.

Learn to use cp and mv to copy and move files and directories, using absolute or relative destination and target paths.

Learn how to use the cp command to copy files in Linux, using relative and absolute paths and the dot shortcut to copy from and to the current directory.

The mv command moves files between directories and can rename them, demonstrated by moving a file from home to downloads and renaming it with a parent directory reference.

Learn how the rm command deletes files, and how the interactive -i option prompts for confirmation before removal, with aliases showing how rm can default to interactive safety.

Learn how rm -rf uses recursive and force options to delete a directory tree and suppress prompts, while warning about potential deletion of important files.

Create an empty directory with mkdir, remove only empty directories with rmdir, and use rm -r or rm -rf for non empty directories, demonstrated with practical terminal examples.

Master the touch command to create new empty files and update a file's timestamp, illustrated by creating new_data_file and updating an existing file's last modified date.

Discover how the wildcard, represented by an asterisk, speeds moving and removing multiple files in the Linux command line, including deleting mp3s with rm.

Learn how the cat command concatenates inputs and prints results to the screen, and view file contents in the terminal with practical examples of single and multiple files.

Learn how to use the less command to view text files from the top, navigate with arrows and page keys, and search for strings to highlight matches like fear.

Explore grep, a tool to filter text from files, search for words, and count occurrences, with options like -i for case-insensitive and -o for printing matches, and support for piping.

Learn how to control command output with pipes and redirection operators, including overwriting and appending to files.

Learn how to use output redirection and piping in Linux, including piping ifconfig output to grep, and redirecting to files with echo, with overwrite and append options.

Learn to use the find command to search for files by name with wildcards and by size in directories, using -name and -size, and view results with ls -lh.

Explore how the du command reports directory trees and file sizes, showing system space allocation; use -s for summarize and -h for human readable with wildcards to inspect multiple items.

Learn how symbolic links and hard links are created with ln, why absolute paths matter, and how a symbolic link behaves like a shortcut to a target file.

Learn how symbolic links can use relative or absolute paths and how moving the target can break them. Understand when to use absolute paths for reliability.

Learn how to create temporary and permanent bash aliases to shorten commands, using the alias syntax, echo to append to ~/.bash_aliases, and reload sessions for changes.

Learn to use vi as a terminal text editor, switching from command mode to insert mode to create or edit files and save or quit with w, q, and wq.

Explore multiple pipes to pass output through cut, grep, head, and tail, extracting fields like the ip address. Build one-line commands and aliases to display the ip address instantly.

Master sed, the stream editor, by performing text substitution with s/old/new/ and global flags, using regular expressions and optional in-place edits with -i or pipes.

Understand Linux permissions in a multi-user system. Use chmod to set read, write, and execute rights, and switch to superuser with su or sudo to manage chown and chgrp.

Experiment with Linux file permissions and ownership, using sudo to become root and change ownership from root to Ibrahim and adjust others' write access.

Explore how a bash script acts as an executable program for the Linux command line, its uses, and when to prefer bash over Perl or Python.

Create a bash hello world script with a shebang, echo hello world, make it executable with chmod, and run it via a relative path or full path.

Learn to create a hello world script with bash variables, define a as Hello world, access it with $a, and print 640 and 7.2 to see hello world 640 7.2.

Learn to perform arithmetic in bash by defining variables a and b and using the dollar sign with parentheses to compute the sum and difference, then echo the results.

Learn how to use conditionals in Bash with the if statement to check conditions, execute actions when true, and take alternatives when not.

Master bash if statements by using relational operators: less than, greater than, less than or equal, greater than or equal, equal, or not equal, using proper spaces and else echo.

Master bash conditional logic by building if, elif, and else blocks to compare A and B and print whether A is greater, less, or equal to B.

Master bash scripting with the if condition, using and (&&) and or (||) operators. The lecture shows reading into variables A and B and testing for John or Mark.

Master the bash if condition for strings by quoting variables and using the equal sign and not equal sign operators to compare names, with notes on numeric comparisons.

Learn to read user input in bash, store it in variables, and compare two numbers with if statements, echoing which is bigger or if they are equal.

Explore loops in bash scripting, introducing two main loop types and how they repeat actions or run the same code on multiple items, enabling automation and efficiency.

Master bash for loops by defining a range from 1 to 10 with two braces and dot dot, and by using backticks to process the output of commands.

Learn how the while loop in bash runs commands while a condition is true, increments a counter with plus one, and exits when the condition becomes false.

Learn to pass arguments to a bash script using positional parameters like $1 and $2, use an if statement to check for -y, and echo appropriate responses.

Define and use functions to organize code and enable reuse, then call named functions to run specific tasks in bash scripting.

Define and use bash functions with a shebang line, including a get_info example that reads name, age, and email, and a square function that echoes the square of a number.

Create a simple bash menu in options.sh using a while loop, read user input, and handle selections with if-else, including invalid choices and exiting.

Explore a simple bash script (initial.sh) that uses functions to obtain ip address, system time, user name, and hostname, with a menu-driven interface for options 1–4 and exit.