Master Linux Shell Arrays: Definition, Access, Modification, and Advanced Tricks

Linux shell scripting is far more powerful than Windows batch processing, especially for handling arrays.

1. Defining an array

a=(1 2 3 4 5)

Parentheses create an array; elements are separated by spaces.

2. Reading and assigning

Length

echo ${#a[@]} # => 5

Use ${#array[@]} or ${#array[*]} to obtain the array length.

Read element

echo ${a[2]} # => 3

echo ${a[*]} # => 1 2 3 4 5

Indexes start at 0; * or @ expands the entire array.

Assign

a[1]=100

echo ${a[*]} # => 1 100 3 4 5

a[5]=100

echo ${a[*]} # => 1 100 3 4 5 100

Assigning to a non‑existent index automatically appends a new element.

3. Deleting elements

unset a[1]

echo ${a[*]} # => 1 3 4 5

Use unset array[index] to remove a specific element; unset array clears the whole array.

4. Special operations

Slice

echo ${a[@]:0:3} # => 1 2 3

echo ${a[@]:1:4} # => 2 3 4 5

The syntax ${array[@]:start:length} returns a slice; wrapping the result in parentheses creates a new array.

Replace

echo ${a[@]/3/100} # => 1 2 100 4 5

The pattern ${array[@]/old/new} performs substitution without altering the original array; to persist the change, reassign the result to the array.

These commands demonstrate that Linux shell arrays are powerful and cover most common use cases.