mkimage-profiles/bin/mktmpdir

#!/bin/sh
# analyze free space, preferring tmpfs over really many gigaz

# hope there aren't spaces in RM's $HOME are they?
DIRS="$TMP $TMPDIR $HOME/hasher /tmp /var/tmp"
MINSIZE=262144		# face control criterion

# pick existing, writeable, >256M free space dirs
# rank them wrt type: tmpfs > realfs > rootfs
choose_tmpdir() {
	for i in $DIRS; do
		[ -d "$i" -a -w "$i" ] || continue
		echo -n "$i "
		df -Tl "$i" | tail -1
	done \
	| sort -unk6 \
	| while read dir dev fstype size used free percent mnt; do
		[ "$free" -gt "$MINSIZE" ] || continue
		[ "$fstype" = "tmpfs" ] && { echo "2 $dir $free"; continue; }
		[ "$mnt" = "/" ] && { echo "0 $dir $free"; continue; }
		echo "1 $dir $free"
	done \
	| sort -n \
	| tail -1 \
	| cut -f2 -d' '
}

DIR="`choose_tmpdir`"
mktemp -d "${1:-tmpdir}.XXXXXXX" --tmpdir="${DIR:-`realpath ..`}"