passing tab separated entries to readarray

Question

Obviously I'm not doing it right, but I think the intended outcome is clear (${#arr[@]}=3)

$ readarray -d "\t" arr < <(printf "%s\t%s\t%s" "x" "y" "z"); echo "${#arr[@]}"
> 1

Answer 1

The shell doesn't know that \t should be a tab. It is looking for a literal \ followed by a t (ignoring the latter as delimiters can only be single bytes (not even characters)):

$ readarray -d "\t" arr < <(printf %s 'x\ty\tz'); echo "${#arr[@]}"
3
$ typeset -p arr
declare -a arr=([0]="x\\" [1]="ty\\" [2]="tz")

For actual tabs, you need to escape like this:

$ readarray -d $'\t' arr < <(printf "%s\t%s\t%s" "x" "y" "z"); echo "${#arr[@]}"
3

Note that your third value above is not delimited. It's fine here because it's not empty, but had it been empty, you'd have gotten:

$ readarray -d $'\t' arr < <(printf "%s\t%s\t%s" "x" "y" ""); echo "${#arr[@]}"
2

To allow any value (that doesn't contain TAB nor NUL characters) including empty ones, you'd want to make sure they are delimited with:

printf '%s\t' "$val1" "$val2" "$val3"

Same as:

printf '%s\t%s\t%s\t' "$val1" "$val2" "$val3"

You may also want to remove the delimiters from the array elements with readarray's -t option.