#!/usr/bin/env sh

# returns a non-colliding temporary directory name
# fallback to /tmp if $XDG_RUNTIME_DIR has less than 1GB of space
free_space="$(df -Pk "$XDG_RUNTIME_DIR" | tr -s ' ' '\t' | cut -f4 | tail -n 1)"
[ $free_space -lt 1000000 ] && XDG_RUNTIME_DIR="/tmp"

while :; do
	prefix="${XDG_RUNTIME_DIR:-/tmp}"
	key=$(tr -cd 'a-z0-9' < /dev/urandom | dd bs=7 count=1) 2> /dev/null
	dir="$prefix/$key"
	[ ! -d "$dir" ] || continue

	echo "$dir" && exit 0
done