How can I assign the last element of an array to a another array?

Question

Let say I have an array $Info whose elements are ;

!    total energy              = -1090.13343774 Ry
!    total energy              = -1090.20757070 Ry
!    total energy              = -1090.24296462 Ry
!    total energy              = -1090.25563488 Ry
!    total energy              = -1090.27085564 Ry
!    total energy              = -1090.27693129 Ry
!    total energy              = -1090.28213580 Ry
!    total energy              = -1090.29131927 Ry

and I want to take its last element , split it with spaces and give to an another array $LastInfo. How can I do that ?

I tried this;

lst=$((${#Info[@]} -1))
IFS=' ' LastInfo=($en[$lst])

But as posted in here the code doesn't work.

Answer 1

With ksh93, bash or zsh

last=( "${arr[@]: -1}" )

That has the advantage over the zsh-style last=( "${arr[-1]}" ) (beside being more portable: to ksh93 and to bash 4.2 or older which don't support the zsh-style syntax) that if $arr is an empty array, $last becomes an empty array as well rather than an array containing one empty element.

Answer 2

1. If your array is called Info, and you're calculating the index of the last element of Info, it doesn't make sense to use it to index into en (a different array).
2. When you do index into an array, you have to use braces;
   not

      $en[$lst]

   but

      ${en[$lst]}

Answer 3

What you probably want to do is:

# given that $Info is a populated array..
Lastinfo=(${Info[-1]})

Whitespace is already a default separator, so each space-separated element of the list entry in the Info array will be an entry in the new LastInfo array.