Bash User Defined Variables

User-defined variables are created by you (the user) in a shell or script to store temporary values, messages, or configurations.

They are not predefined by the system.

prabhumanyam@PrabhuPC:~$ mine="Sandeep"

prabhumanyam@PrabhuPC:~$ echo $mine

Sandeep

prabhumanyam@PrabhuPC:~$ unset mine

prabhumanyam@PrabhuPC:~$ echo $mine

prabhumanyam@PrabhuPC:~$ mine="Sandeep"

prabhumanyam@PrabhuPC:~$ readonly mine

prabhumanyam@PrabhuPC:~$ unset mine

-bash: unset: mine: cannot unset: readonly variable

prabhumanyam@PrabhuPC:~$ name = "Prabhu"

Command 'name' not found, did you mean:

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Rules for User-Defined Variables

No spaces around =

✅ name="Prabhu"

❌ name = "Prabhu"

1. Variable names can contain letters, numbers, and underscores (_)
2. Variable names cannot start with a number
3. Use $ to access the value — e.g. echo $name
4. By default, variables are local to the current shell or script
5. Use export to make them available to child processes.

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prabhumanyam@PrabhuPC:~$ cat uservariable.sh

#!/bin/bash

# 🧩 USER-DEFINED VARIABLES

echo "============================================="

echo "        👤 USER-DEFINED VARIABLES"

echo "============================================="

# Define variables

name="Prabhu"

role="QA Engineer"

experience="7 Years"

domain="ETL / Big Data Testing"

company="Oracle Financial Services"

location="Bangalore"

# Exported variable (can be used by child scripts)

export greeting="Hello, $name! Welcome to $company."

# Arithmetic example

a=10;

b=30;

sum=$((a+b))

# Display user-defined variable values

echo "Name        : $name"

echo "Role        : $role"

echo "Experience  : $experience"

echo "Domain      : $domain"

echo "Company     : $company"

echo "Location    : $location"

echo "Sum Example : $a + $b = $sum"

echo "Greeting    : $greeting"

echo "My Name is : $name and My role in company is : $role"

echo "---------------------------------------------"

prabhumanyam@PrabhuPC:~$ sh uservariable.sh

=============================================

        👤 USER-DEFINED VARIABLES

=============================================

Name        : Prabhu

Role        : QA Engineer

Experience  : 7 Years

Domain      : ETL / Big Data Testing

Company     : Oracle Financial Services

Location    : Bangalore

Sum Example : 10 + 30 = 40

Greeting    : Hello, Prabhu! Welcome to Oracle Financial Services.

My Name is : Prabhu and My role in company is : QA Engineer

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