A samba dfree script I wrote a while back for correctly reporting the total and free space on zfs pools and any other fs if not zfs (read: it doesn't break on non zfs filesystems)

dfree.sh

#!/usr/bin/env zsh
maybe_pool="$(df ${1} | awk -F'[\t/ ]' 'END{print $1}')"
if (zfs list -Hp "${maybe_pool}"  >/dev/null 2>&1); then
    pool_name="$(zfs list -Hp "${maybe_pool}" | awk -F"[\t/]" '{print $1}')"
    zpool list -Hp "${pool_name}" | cut -f 2-4 | read total used zpoolfree
    realfree="$(zfs list -Hp "${pool_name}" | cut -f 3)"
    python3 -c "import bigfloat; print(f'{int(bigfloat.div(${total}, 1024))} {int(bigfloat.div(${realfree}, 1024))}')"
else
        df "${1}" | tail -1 | awk '{print $2" "$4}'
fi