Considering an array,has say 5 elements
"${#my_array[@]}"
As this gives the array size of 5. How to get less then 1 (i.e. array_size-1)
"${#my_array[@]}-1"
#and
"${#my_array[@]-1}"
doesn't work
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U&L: How to do integer & float calculations, in bash or other languages/frameworks?kvantour– kvantour2020-07-27 13:30:10 +00:00Commented Jul 27, 2020 at 13:30
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1 Answer
If what you are trying to do is reference the array from the end, use negative indexes.
$: my_array=( a b c d e )
$: echo "${#my_array[@]}"
5
$: echo "${my_array[-1]}"
e
$: echo "${my_array[-2]}"
d
If you just need the numeric reference of the last element, please carefully read the links provided, but here's an example.
$: lastIndex=$(( ${#my_array[@]} - 1 ))
$: echo $lastIndex
4
$: echo ${my_array[$lastIndex]}
e
or without the $,
$: echo ${my_array[lastIndex]} # arithmetic context recognizes varnames
e
2 Comments
glenn jackman
Note that the index of an numerically indexed array is an arithmetic expression, so you can do this:
${my_array[ ${#my_array[@]} - 2 ]}, but the negative indices are much more readable.glenn jackman
Also, because the index is an arithmetic expression, you can omit the
$: ${my_array[lastIndex]}