Accessing variables ($var and ${var}) in Bash Scripting - Step-by-Step Execution

Concept Flow - Accessing variables ($var and ${var})

Define variable var=World

↓

Access with $var

→Print value

↓

Access with ${var}

→Print value

↓

Use in strings or with suffixes

↓

Output final combined string

This flow shows how a variable is defined and accessed using $var and ${var}, including usage in strings.

Execution Sample

Bash Scripting

var=World

echo Hello $var

echo Hello ${var}!

name=User

echo Welcome ${name}123

This script defines variables and prints them using $var and ${var} syntax, showing how to append text safely.

Execution Table

Step	Command	Variable Access	Output
1	var=World	Set var
2	echo Hello $var	$var	Hello World
3	echo Hello ${var}!	${var}	Hello World!
4	name=User	Set name
5	echo Welcome ${name}123	${name} with suffix	Welcome User123
6	echo Welcome $name123	$name123 (undefined)	Welcome

💡 Script ends after printing all lines; last echo shows difference between $var and ${var} with suffix.

Variable Tracker

Variable	Start	After Step 1	After Step 4	Final
var	undefined	World	World	World
name	undefined	undefined	User	User

Key Moments - 2 Insights

Why do we use ${var} instead of $var when adding text right after the variable?

Using ${var} clearly marks the variable name boundary, so the shell knows where the variable ends and the text begins, as shown in step 5 vs step 6 in the execution_table.

What happens if we write $name123 instead of ${name}123?

The shell looks for a variable named 'name123' which is undefined, so it prints nothing for that part, as seen in step 6 output.

Visual Quiz - 3 Questions

Look at the execution_table, what is the output of step 3?

A Hello World

B Hello World!

C Hello ${var}!

D Hello !

💡 Hint

Check the Output column for step 3 in the execution_table.

At which step is the variable 'name' first set?

A Step 4

B Step 2

C Step 1

D Step 5

💡 Hint

Look at the Command and Variable Access columns to see when 'name' is assigned.

If we change echo Welcome $name123 to echo Welcome ${name}123, what changes in output?

A Output becomes 'Welcome '

B Output becomes 'Welcome ${name}123'

C Output becomes 'Welcome User123'

D No change in output

💡 Hint

Compare outputs of step 5 and step 6 in the execution_table.

Concept Snapshot

Accessing variables in bash:
- Use $var to get variable value.
- Use ${var} to clearly mark variable name.
- ${var} helps when adding text right after variable.
- Without braces, shell may misinterpret variable name.
- Always use braces to avoid confusion.

Full Transcript

This lesson shows how to access variables in bash scripts using $var and ${var}. We start by defining variables 'var' and 'name'. Then we print them using both $var and ${var} syntax. Using ${var} is important when you want to add text immediately after the variable name, so the shell knows where the variable ends. For example, echo Hello ${var}! prints 'Hello World!' while echo Hello $var! also works here because the exclamation mark is separate. But echo Welcome $name123 tries to find a variable named 'name123' which is not set, so it prints nothing after 'Welcome '. Using echo Welcome ${name}123 correctly prints 'Welcome User123'. This helps avoid confusion and errors in scripts.