Introduction to Linux

Linux is a free open-source operating system that works just like Windows and Mac OS X. It is a Unix clone, multi-tasking and a multi-user operating system that was developed by Linus Torvalds with the collaboration of the developers around the world.

Linux - A Kernel, not an Operating System

Strictly speaking, Linux is a kernel, not an entire operating system. A kernel provides access to computer hardware and a controlled access to system resources such as:

• Security and firewall
• GNU libraries and utilities
• Other management and installation scripts
• Logged in users
• Running and loading programs to memory
• Networking systems
• Files and data
• Process management
• Device management
• I/O management

Shell Classification

• Command line shell
• Graphical shell

Introduction to Linux Shell

A shell is an environment provided for the user to interact with the machine.

Shell is not a part of Linux kernel, but it uses the kernel to execute programs, create files etc. Several command line shells are available for Linux including:

• BASH ( Bourne-Again SHell ) - It’s the default open source shell on many Linux distributions today
• CSH (C SHell) - The C shell’s syntax and usage are very similar to the C programming language
• KSH (Korn SHell) - It is a high-level interactive command language
• TCSH - It is an enhanced but completely compatible version of the Berkeley UNIX C shell (CSH)
• ZSH - It is an interactive shell that incorporates features of other Linux shells including some unique ones too
• Fish (Friendly Interactive Shell) - It is a smart and user-friendly interactive shell along with some other features