Array slicing in Bash Scripting - Step-by-Step Execution

Concept Flow - Array slicing

Define array

↓

Specify slice start and length

↓

Extract slice

↓

Use or display slice

↓

End

Start with an array, choose where to slice and how many elements, then extract and use that slice.

Execution Sample

Bash Scripting

arr=(apple banana cherry date elderberry)
start=1
length=3
slice=(${arr[@]:start:length})
echo "${slice[@]}"

Extracts 3 elements from index 1 of the array and prints them.

Execution Table

Step	Action	Array State	Slice Indices	Slice Result	Output
1	Define array	[apple, banana, cherry, date, elderberry]	-	-	-
2	Set slice start=1, length=3	-	start=1, length=3	-	-
3	Extract slice	-	start=1, length=3	[banana, cherry, date]	-
4	Print slice	-	-	[banana, cherry, date]	banana cherry date
5	End	-	-	-	-

💡 Slice extracted and printed; script ends.

Variable Tracker

Variable	Start	After Step 2	After Step 3	Final
arr	[apple, banana, cherry, date, elderberry]	[apple, banana, cherry, date, elderberry]	[apple, banana, cherry, date, elderberry]	[apple, banana, cherry, date, elderberry]
slice	undefined	undefined	[banana, cherry, date]	[banana, cherry, date]
start	undefined	1	1	1
length	undefined	3	3	3

Key Moments - 3 Insights

Why does the slice start at index 1, not 0?

In the execution_table row 2, start=1 means slicing begins from the second element because bash arrays are zero-indexed.

What happens if the slice length is longer than remaining elements?

If length exceeds available elements, bash returns all elements from start to end without error, as shown in row 3 if length was larger.

Why do we use parentheses around the slice extraction?

Parentheses create a new array from the slice, ensuring slice is an array variable, as shown in row 3.

Visual Quiz - 3 Questions

Look at the execution_table at step 3, what elements are in the slice?

A [date, elderberry]

B [banana, cherry, date]

C [apple, banana, cherry]

D [apple, elderberry]

💡 Hint

Check the 'Slice Result' column at step 3 in the execution_table.

At which step is the slice printed to output?

A Step 4

B Step 3

C Step 2

D Step 5

💡 Hint

Look for the 'Print slice' action and its output in the execution_table.

If we change start to 2 and length to 2, what will the slice contain?

A [banana, cherry]

B [date, elderberry]

C [cherry, date]

D [apple, banana]

💡 Hint

Refer to variable_tracker for start and length values and how slicing works.

Concept Snapshot

Array slicing in bash:
arr=(a b c d e)
slice=(${arr[@]:start:length})
start = index to begin (0-based)
length = number of elements to extract
slice is a new array with selected elements

Full Transcript

This visual trace shows how to slice arrays in bash scripting. First, an array is defined with elements. Then, we choose a start index and length for the slice. Using the syntax ${arr[@]:start:length}, we extract a portion of the array. Parentheses around this expression create a new array variable holding the slice. Finally, we print the slice elements. The trace follows each step, showing variable values and outputs, helping beginners see how array slicing works in bash.