Shell Variables & Environment

HOME --- ECHO VS PRINTF

Variables are used to store data and configuration option. There are two types of variables :

System Variables : Created and maintained by Linux BASH. Usually defined in Capital Letters.

Any of the these command can be used to check for existing system variables.

set
env
printenv

Some important System Variables:


BASH_VERSION	Version of BASH
HOSTNAME	Name of our device
CDPATH	Search path for cd command
HISTFILE	File where history is stored
HISTFILESIZE	Maximum lines in history file
HISTSIZE	Number of commands to remember for history
HOME	Current user's home directory
PATH	Search path for command

User-Defined Variable : Created and maintained by user. It is suggested to avoid a variable name wilth all uppercase.

Notation to be followed to assign value to a vriable.
```
variableName=value
```

Variable Naming Convention

We can also define null variable in BASH using the notation below,

variableName=
variableName=""

declare -TYPE variable=value

Here type can be of two type,