Обновление скрипта резервного копирования

Обновил скрипт для резервного копирования. Убрал вызов bc, вынес всё в отдельные функции, причесал код, чтобы ShellCheck был счастлив:

#!/usr/local/bin/bash

BACKUP_ROOT=/var/backups/manual/
BACKUP_DIR="$BACKUP_ROOT"$(date +"%Y-%m-%d/%H-%M")
PREFIX=$(date +"%Y%m%d_%H%M")
LIMIT=$((4*1024*1024))

exit_on_error() {
    exit_code=$?
    if [ $exit_code -ne 0 ]; then
        >&2 echo -e "FAIL"
        exit $exit_code
    fi
}

print_used_space() {
    printf "Used space: "
    SIZE=$(du -sB 1 $BACKUP_ROOT | cut -f 1)
    printf "%sMb(%s%%)\n" "$((SIZE / 1024))" "$((SIZE * 100 / LIMIT))"
}

backup_etc() {
    FILENAME="$PREFIX"_etc.tar.bz2
    printf "Creating %s .. " "$FILENAME"
    if /usr/bin/tar -Pjcf "$BACKUP_DIR"/"$FILENAME" /etc /usr/local/etc /home /var/db/ports /var/named/etc/namedb /root/scripts > /dev/null 2>&1; then
        printf "OK\n"
    else
        exit_on_error
    fi
}

backup_site() {
    FILENAME="$PREFIX"_www.tar.bz2
    printf "Creating %s .. " "$FILENAME"
    if /usr/bin/tar -Pjcf "$BACKUP_DIR"/"$FILENAME" /usr/local/www > /dev/null; then
        printf "OK\n"
    else
        exit_on_error
    fi
}

backup_db() {
    FILENAME="$PREFIX"_db.sql.bz2
    printf "Creating %s .. " "$FILENAME"
    if /usr/local/bin/mysqldump --login-path=backup --opt --all-databases --triggers --routines --events | bzip2 -c > "$BACKUP_DIR"/"$FILENAME"; then
        printf "OK\n"
    else
        exit_on_error
    fi
}

remove_old_files() {
    removed=0
    for days in $(seq 100 -1 0)
    do
        SIZE=$(du -sB 1 $BACKUP_ROOT | cut -f 1)
        if [[ $SIZE -le $LIMIT ]]; then
            break
        fi
        if [[ -z "$(find $BACKUP_ROOT -type f -mtime +"$days")" ]]; then
            continue
        fi
        printf "Removing files older than %d days:\n" "$days"
        find $BACKUP_ROOT -type f -mtime +"$days"d -delete -print
        find $BACKUP_ROOT -empty -type d -delete -print
        removed=1
    done

    if [ $removed -ne 0 ]; then
        true
        return
    fi

    false
}

if [ ! -d "$BACKUP_DIR" ]; then
        mkdir -p "$BACKUP_DIR"
fi

backup_etc
backup_site
backup_db
print_used_space
remove_old_files && print_used_space
true