cleanup.sh

#!/bin/bash
set -e

prefix=/mnt/usb/
# delete dir with size < 5 MB 
#DIRRM=`find /mnt/usb -mindepth 1 -maxdepth 1 -type d -exec du -ks {} + | awk '$1 <= 50000' | cut -f 2-`
#IFS='
#'
#for i in $DIRRM; do
#	rm -rf $i
#done
#find /mnt/usb/ -type d -empty -delete

shopt -s nullglob
dir_array=(/mnt/usb/*)
shopt -u nullglob # Turn off nullglob to make sure it doesn't interfere with anything later
#printf "dir_array=%s\n" "${dir_array[@]}"  # Note double-quotes to avoid extra parsing of funny characters in filenames

IFS=$'\n' read -r -d '' -a tr_array < <( transmission-remote -l | sed '1d;$d' && printf '\0' )
#printf "tr_array=%s\n" "${tr_array[@]}"  # Note double-quotes to avoid extra parsing of funny characters in filenames

# Haven't figured out how to not include /mnt/usb in the above glob output, and so have to prefix the same below
tr_names_array=()
for i in "${tr_array[@]}"; do
	name=$(echo "$i" | cut -c 71-)
	tr_names_array+=($prefix"$name")
done
#printf "tr_names_array=%s\n" "${tr_names_array[@]}"  # Note double-quotes to avoid extra parsing of funny characters in filenames

# Without this, this file also would get deleted in the loop
tr_names_array+=('/mnt/usb/'`basename "$0"`)

# delete dirs/files which are not in transmission torrent list
for i in "${dir_array[@]}"; do
	if ! [[ "${tr_names_array[*]}" =~ "$i" ]]; then
		rm -rf "$i"
	else
		dir_size=`du -sm "$i" | cut -f1`
		[[ dir_size -lt 5 ]] && printf "%s has size < 5 MB, consider deleting it. Actual size is %d MB.\n" "$i" $dir_size
	fi
done

# delete transmission torrent not in dirs/files in /mnt/usb
for i in "${tr_array[@]}"; do
	name=$(echo "$i" | cut -c 71-)
	if ! [[ "${dir_array[*]}" =~ "$name" ]]; then
		# get torrent id
		[[ "$i" =~ ^[^0-9]*([0-9]+)\* ]] && torrent="${BASH_REMATCH[1]}"
		transmission-remote --torrent "$torrent" --remove-and-delete
	fi
done