Store Data
Store values that can be reused throughout the script.
Shell Script · Variables
Shell Scripting · Lesson 6
Variables
Understand variables in shell scripting. System and user defined variables. Rules for naming variables. Using variables in real automation scripts.
What Are Variables?
Variables are used to store data that can be reused throughout a script. A variable can hold text, numbers, or command output.
In shell scripting, variables are created dynamically and do not require explicit data types.
Why Use Variables?
Avoid Repetition
Change value once and reuse it everywhere.
Dynamic Behavior
Scripts behave dynamically based on variable values.
Types of Variables
- Local Variables
- Environment Variables
- Read-only (Constant) Variables
Variable Examples
1. Defining a Variable
Variables are created by assigning a value without spaces around '='.
terminal — bash
variablesname="Linux"
echo $name
2. Numeric Variable Example
Variables can store numbers and be used in calculations.
terminal — bash
variablesnum=10
echo $num
3. Overwriting a Variable
Variables can be reassigned with new values.
terminal — bash
variablescourse="Shell"
echo $course
course="Linux"
echo $course
4. Read-only (Constant) Variable
Use readonly to make a variable constant.
terminal — bash
variablesreadonly PI=3.14
echo $PI
PI=3.1415 # This will cause an error
5. Environment Variable
Environment variables are available to child processes.
terminal — bash
variablesexport CITY="Delhi"
echo $CITY
Best Practices
Good Practices
- Use meaningful variable names.
- Avoid spaces around '='.
- Use uppercase for constants.
- Quote variables to prevent word splitting.
Practice Task – Variables
- Create a variable named
nameand print it. - Create a variable
ageand update its value. - Create a constant variable using
readonly. - Export a variable and verify it using
env.
Next lesson: User Input (read command)