Store expanded array in a variable using a brace expansion

Question

I want to store node1 node2 node3 in a variable so that it may be used as an input to other scripts.

However, I want to do so by using brace expansion given by bash like so: node{1..3}

I tried to have a variable nodes=node{1..3}, but when I use it as an argument ($nodes) to the script, it gets picked up literally and doesn't expand.

Answer 1

To assign to an array, put the elements in parentheses:

nodes=(node{1..3})

When using the array, you need to tell bash explicitly that you want to expand it as an array.

mycommand "${nodes[@]}"

Due to a design quirk of arrays in ksh and bash, $node is the first element of the array, you need to explicitly ask for all the elements with the [@] indexation. As always, you need double quotes around the variable expansion; with [@], each element is placed into a separate word.

See the bash manual for more information.

node=node{1..3} doesn't work because brace expansion only happens in contexts that allow multiple words. An assignment to a scalar (string) variable only allows a single word. You also only get a single word when expanding the variable, since Bash does brace expansion before variable expansion.

Answer 2

To the consideration of expert users:

$ mapfile -t arr < <(printf "%s\n" node{1..3})
$ printf "%s\n" "${arr[@]}"
node1
node2
node3

Source

Answer 3

Found the answer after looking at this question: What is the rationale behind $array not expanding the whole array in ksh and bash?

nodes=$(echo nodes{1..3})