Shell scripting consists of set of commands to perform a task.

Different types of shells:

  1. bash
  2. sh
  3. ksh
  4. tsh
  5. fish
  6. zsh (Extended version of bash with more advanced features)

What is my shell type?

echo $0

How to check supported shells?

cat /etc/shells

What is shebang?

It specifies which interpreter should be used to execute the script.

#!/bin/bash

Basic shell script

#!/bin/bash
echo "hello world!"

How to execute script?

Make sure script have execute permission rwx.
1- ./file.sh
2- path/file.sh
3- bash file.sh

How to add comments?

1- single line comment 

#comment

2- Multiline comment

<

Variables:

How to use variables?

#!/bin/bash
person="Arbab Anjum"
hostName=$(hostname)
readonly role="superadmin"

echo $person is using $hostName and role is $role

------
> Output: Arbab Anjum is using ubuntu and role is superadmin

Array:

How to define and get value of an array?

Set Value:

myArray = (1 2 3 Hello "World");

Get Value:

echo "${myArray[0]}"
echo "${myArray[1]}"

How to find length of an array?

echo "${#myArray[*]}"

How to get specific values?

echo "${myArray[*]:1}"
echo "${myArray[*]:1:2}" // from index 1, get 2 values

How to update an array?

myArray+=(New 7 8)