1. is open source software

2. provides easy access to a powerful and scriptable command-line interface (CLI)

3. is a modular operating system that allows you to easily replace or remove components

The three main components of an operating system they are the kernel, shell, and file system

Make requests to the kernel and receive resources, such as memory, CPU, and disk, in return. The kernel also abstracts the complicated details away from the application

is an interactive interface that allows users to execute other commands and utilities in Linux and other UNIX-based operating systems

are a lot more powerful than the Windows command line, because they function as a scripting language as well, with a complete set of tools

is a type of interpreter that processes shell commands. It is a Unix shell and command language

Bash is a Unix shell and command language written by

is a hierarchy of directories and files with the root / directory at the top of the directory tree. It is a structure created on a disk partition consisting of tables defining the locations of directories and files.

Is an operating system made from a software collection that is based upon the Linux kernel and, often, a package management system.

takes a source-centric view of software. The open source philosophy is that you have a right to obtain the software and to modify it for your own use. Linux adopted this philosophy to great success

1. Copyleft licenses that are designed to encourage keeping code open source.

2. Permissive licenses that are designed to maximize code reusability.

is a text interface to your computer. Also known as shell, terminal, console, command prompts and many others, is a computer program intended to interpret commands

The default shell for users in Red Hat Enterprise Linux and CentOS

A software program that when executed on the command line, performs an action on the computer.

Also called built-in commands, these commands are built-in to the shell itself. A good example is the cd (change directory) command as it is part of the Bash shell.

These commands are stored in files that are searched by the shell. If you type the ls command, then the shell searches through a predetermined list of directories to try to find a file named ls that it can execute.

can override a built-in command, function, or a command that is found in a file. can be useful for creating new commands built from existing functions and commands.

can also be built using existing commands to either create new commands, override commands built-in to the shell or commands stored in files.

What are the Sources of Commands?

allows the user to view the contents of a directory. It lists the files and directories. This displays the contents of the current working directory by default

clears the terminal screen

It allows users to find the path of the current working directory or folder they are in

Used to navigate through the Linux files and directories. You will have to write the full path or the name of the directory to use this command

Used to copy files from the current directory to a different directory

Used to move a file from a given directory to a different directory. It helps programmers to organize data easily. You can also use this command to rename files. The file or directory that is moved is deleted from the working directory

deletes directories as well as the contents within them. This command needs to be used carefully as it deletes everything.

allows users to delete a directory, provided that the directory is empty. You will need to ensure that there is no file or subdirectory under the directory that you want to delete

set of characters can be enclosed that will be used to match exactly one character.

can be used to match any string, including the empty string

A _______ is essentially a symbol which may be used to substitute for one or more characters

is a feature provided by the UNIX/Linux shell to represent multiple filenames by using special characters called wildcards with a single file name

clears entire content of the history file

Log in shell & Interactive shell

/etc/profile

~/.bash_profile

~/.bashrc

/etc/bashrc

This command prints detailed information about your Linux system. The information includes machine name, kernel, operating system, and more. Different options tell about different pieces of information

Used to check your connection to a server. It checks the reachability of a host on an Internet Protocol (IP) network"

can be used to specify something for the command to act upon. Following a command, any desired _______ are allowed or are required depending on the command

can be used to specify something for the command to act upon. Following a command, any desired _______ are allowed or are required depending on the command

you can create a new blank file with the given name.

enables users to locate a file. If you don't remember the exact file name, you can use the -i argument to make it case-insensitive

It enables users to run some commands as a super user or System Administrator that normal users cannot do. You can run such commands that need elevated rights on a Linux system

users can get the information related to file systems about total space and available space. You can get a report on display the size, available space, and system's disk space usage, and more. This command shows the result in percentage and KBs

shows how much space a file or a directory takes.

you can change the ownership of a file or folder to the specified username

displays a text or a string to the standard output or a file

This command allows users to view the first lines of any text file. It shows the first ten lines by default.

This command shows the last ten lines of a text file

This command prints detailed information about your Linux system. The information includes machine name, kernel, operating system, and more. Different options tell about different pieces of information

uname stands for

shows the previously used commands. It displays the information about the commands executed by a user

This command is used to check the reference manual pages for commands or programs

It is used to add or remove a user on a Linux server

is used to display the contents of a file

Arguments that contain unusual characters like spaces or non-alphanumeric characters will usually need to be quoted, either by enclosing them within double quotes or single quotes

can be used with commands to expand or modify the way a command behaves. They can be specified after the command name

can be used with commands to expand or modify the way a command behaves. They can be specified after the command name

A variable that can only be accessed from a specific portion of a program. Is only available to the shell in which it was created

is your way of telling Linux to finish the current word you are typing

prevent the shell from interpreting any special characters

will prevent the shell from interpreting some of these special characters

will prevent the shell from interpreting some of these special characters

contains a list of directories that are used to search for commands entered by the user. When the user types a command and then presses the Enter key, the directories are searched for an executable file that matches the command name.

specifies the location of a file or directory from the top-level directory through all of the subdirectories to the file or directory. Always starts with the / character

specifies the location of a file or directory from the top-level directory through all of the subdirectories to the file or directory. Always starts with the / character

Adds a directory to PATH