Mutable list or array structure in Bash? How can I easily append to it?
$ arr=(1 2 3)
$ arr+=(4)
$ echo ${arr[@]}
1 2 3 4
Since Bash uses sparse arrays, you shouldn't use the element count ${#arr} as an index. You can however, get an array of indices like this:
$ indices=(${!arr[@]})
foo=(a b c)
foo=("${foo[@]}" d)
for i in "${foo[@]}"; do echo "$i" ; done