Terminal and Shell in Linux

This post explains the term Terminal, Shell and Bash used in Linux. After reading this post you should be able to distinguish between these conmanly related terms.

Terminal

Terminal is a program called a terminal emulator. It opens a window and lets you interact with the shell. Various types of terminal emulators are supported by Linux distributions. Some of them are gnome-terminal, konsole, rxvt, kvt, nxterm, and eterm.

A terminal window has shell prompt that contains user name followed by the name of the machine. For example

Shell

A Shell is a command line interface (CLI) between a users and the kernel. It is a program that takes commands from the keyboard and gives them to the operating system to perform. Shell in Linux can be used to run programs, work with file systems and so on. It actually processes commands and returns output.

On most Linux systems a program called bash (which stands for Bourne Again Shell) acts as the shell program. Besides bash, other shell programs available for Linux systems include: ksh, tcsh and zsh.

Bash

Bash is largely compatible with sh and incorporates useful features from the Korn shell and the C shell. Bash is quite portable, independently-supported ports exist for MS-DOS, OS/2, and Windows platforms. C shell has interface similar to the C language.

Example

Following command will display what shell the terminal opened with. In the below example, $SHELL is environment variable.

root@tryit-evolving:~#echo $SHELL
/bin/bash

Below command find out what shell you are currently in

root@tryit-evolving:~# ps -p $$
  PID TTY          TIME CMD
  144 pts/0    00:00:00 bash

Above shows that the shell is bash. Bellow example illustrate how to find the name of the current.

root@tryit-evolving:~# echo $0
bash