Local variables (local keyword) in Bash Scripting - Step-by-Step Execution

Concept Flow - Local variables (local keyword)

Start function

↓

Declare local variable

↓

Use local variable

↓

Function ends

↓

Local variable destroyed

↓

Return to main script

↓

Local variable not accessible here

When a function starts, it creates a local variable that exists only inside it. After the function ends, the local variable disappears and cannot be used outside.

Execution Sample

Bash Scripting

my_func() {
  local x=5
  echo "Inside function: x=$x"
}
my_func

echo "Outside function: x=$x"

This script shows a local variable x inside a function and tries to access it outside.

Execution Table

Step	Action	Variable x Value	Output
1	Function my_func called	undefined
2	Declare local x=5 inside function	5
3	Print x inside function	5	Inside function: x=5
4	Function my_func ends, local x destroyed	undefined
5	Print x outside function	undefined	Outside function: x=

💡 Function ends, local variable x is destroyed and not accessible outside

Variable Tracker

Variable	Start	After Step 2	After Step 4	Final
x	undefined	5	undefined	undefined

Key Moments - 2 Insights

Why can't we see the value of x outside the function?

Because x is declared with local inside the function (see step 2 and 5 in execution_table), it only exists inside the function and is destroyed when the function ends.

What happens if we declare x without local inside the function?

Then x becomes a global variable and keeps its value outside the function, unlike the local variable shown in step 4 and 5.

Visual Quiz - 3 Questions

Look at the execution_table, what is the value of x inside the function after declaration?

A undefined

B 0

C 5

D null

💡 Hint

Check step 2 and 3 in the execution_table where x is set and printed inside the function.

At which step does the local variable x get destroyed?

A Step 4

B Step 3

C Step 5

D Step 1

💡 Hint

Look at the execution_table row describing function end and variable destruction.

If we remove the local keyword, what will be the output at step 5?

A Error

B Outside function: x=5

C Outside function:

D Outside function: undefined

💡 Hint

Without local, x becomes global and keeps its value after function ends (compare step 5 output).

Concept Snapshot

local keyword in bash creates variables only inside functions
Local variables disappear after function ends
Outside function, local variables are not accessible
Use local to avoid overwriting global variables
Without local, variables are global by default

Full Transcript

This visual execution shows how the local keyword in bash scripting works. When a function starts, declaring a variable with local means it only exists inside that function. The variable x is set to 5 inside the function and printed there. After the function ends, the local variable x is destroyed and cannot be accessed outside. Trying to print x outside the function shows nothing because x does not exist there. This prevents accidental changes to global variables. If local is removed, x becomes global and keeps its value outside the function. This trace helps beginners see how local variables behave step-by-step.