zfscheck.sh for FreeBSD

#!/bin/sh
#
# Written by nka. Modified by Maurizio.
# After debugging comment the next 2 lines, and the last one.
#exec >>/var/log/zfscheck.log 2>&1
#set -xu
email=mail@example.com
max_cap=80

if ! zpool status -x | grep 'all pools are healthy' > /dev/null 2>&1; then
    { date; echo; hostname; echo; zpool status -xv; } | mail -s \
    "Disk failure in: $(hostname)" $email
else
    cap=$(zpool list -H -o capacity | cut -d'%' -f1)
    for line in ${cap}; do
    if [ "$line" -gt $max_cap ]; then
        { date; echo; hostname; echo; zpool list -v; } \
        | mail -s "Disk capacity exceed $max_cap% in: $(hostname)" \
        $email
        break
    fi
    done
fi
#set +xu