Help: Bad array subscript

[perara-chen]

Please fill out this template

Error accessing last element from an array

Additional context

I'm having problem when accessing the last item from an array. I followed exactly the same as written in the book. Can someone explain me if I did something wrong? Thanks.

My script:

#!/bin/bash

my_array=("value 1" "value 2" "value 3" "value 4")

# Access item 1
echo ${my_array[1]}

# Access the last item
echo ${my_array[-1]}

# Access all the items
echo ${my_array[@]}

# Output total number of elements in the array
echo ${#my_array[@]}

Shell output:

value 2
script1.sh: line 9: my_array: bad array subscript

value 1 value 2 value 3 value 4
4

[bobbyiliev]

Hi there,

What version of bash are you using?

bash --version

Note that unsetting with negative index were only added in bash 4.3.

[perara-chen]

Thank you @bobbyiliev. Your pointer solved the problem. I forgot that I was using Apple's age-old bash. I ran the script on my Linux VM with bash 5.1.8 and everything worked well and the problem is solved. Thank you.

Apple's bash

GNU bash, version 3.2.57(1)-release (arm64-apple-darwin22)
Copyright (C) 2007 Free Software Foundation, Inc.

Script

#!/bin/bash

my_array=("value 1" "value 2" "value 3" "value 4")

# Access item 1
echo ${my_array[1]}

# Access the last item
echo ${my_array[-1]}

# Access all the items
echo ${my_array[@]}

# Output total number of elements in the array
echo ${#my_array[@]}

Output

value 2
value 4
value 1 value 2 value 3 value 4
4