for loop (list-based) in Bash Scripting - Step-by-Step Execution

Concept Flow - for loop (list-based)

Start

↓

Define list

↓

Pick first item

↓

Execute loop body

↓

More items?

No→End loop

Yes↓

Pick next item

↩Back to Execute loop body

The loop picks each item from the list one by one and runs the commands inside the loop for each item.

Execution Sample

Bash Scripting

items=(apple banana cherry)
for item in "${items[@]}"
do
  echo "$item"
done

This script loops over a list of fruits and prints each fruit on its own line.

Execution Table

Iteration	item value	Action	Output
1	apple	Print item	apple
2	banana	Print item	banana
3	cherry	Print item	cherry
-	-	No more items, exit loop	-

💡 All items processed, loop ends.

Variable Tracker

Variable	Start	After 1	After 2	After 3	Final
item	undefined	apple	banana	cherry	cherry

Key Moments - 3 Insights

Why does the loop stop after the last item?

The loop checks if there are more items in the list. When no items remain (see last row in execution_table), it stops.

What if the list is empty?

If the list is empty, the loop body never runs because there are no items to pick, so no output is produced.

Why do we use "${items[@]}" instead of just "$items"?

Using "${items[@]}" expands each list element separately, so the loop gets each item individually. Using "$items" would treat the whole list as one string.

Visual Quiz - 3 Questions

Look at the execution table, what is the value of 'item' during iteration 2?

A banana

B apple

C cherry

D undefined

💡 Hint

Check the 'item value' column in the second row of the execution_table.

At which iteration does the loop stop running?

A After iteration 1

B After iteration 3

C After iteration 2

D It never stops

💡 Hint

Look at the exit_note and the last row in execution_table.

If the list was empty, what would the output be?

A apple banana cherry

B Error message

C No output

D Loop runs once with empty item

💡 Hint

Refer to the key_moments explanation about empty lists.

Concept Snapshot

for item in "${items[@]}"; do
  commands using $item
 done

- Loops over each item in the list
- Runs commands once per item
- Stops after last item
- Use "${items[@]}" to get each element separately

Full Transcript

This visual shows how a bash for loop works with a list. The loop starts by defining a list of items. Then it picks the first item and runs the commands inside the loop body using that item. It repeats this for each item in the list. When there are no more items, the loop stops. The variable 'item' changes each iteration to the current list element. If the list is empty, the loop does not run at all. Using "${items[@]}" ensures each item is handled separately. This is a simple way to repeat actions for each element in a list in bash scripting.