Bash arrays and negative subscripts, yes or no?

Question

The GNU bash manual tells me

An indexed array is created automatically if any variable is assigned to using the syntax

name[subscript]=v         


        

Answer 1

According to Greg Wooledge's wiki, (which links to the bash changelog) the negative index syntax was added to bash in version 4.2 alpha.

Answer 2

The negative subscript works perfectly fine for me on my computer with Ubuntu 14.04 / GNU bash version 4.3.11(1) however it returns:

line 46: [-1]: bad array subscript

When I try to run the same script on 4.2.46(1). I

Answer 3

If you just want the last element

$ echo ${muh[*]: -1}
2

If you want next to last element

$ echo ${muh[*]: -2:1}
bleh

Answer 4

Old bashes (like the default one on Macs these days) don't support negative subscripts. Apart from the "substring expansion" used in the accepted answer, a possible workaround is to count the desired index from the array start within the brackets:

$ array=(one two three)
$ echo "${array[${#array[@]}-1]}"
three

With this approach, you can pack other parameter expansion operations into the term, e.g. "remove matching prefix pattern" th:

$ echo "${array[${#array[@]}-1]#th}"
ree

Answer 5

If you do man bash the section on arrays does not list this behavior. It might be something new (gnu?) in bash.

Fails for me in CentOS 6.3 (bash 4.1.2)