Bash version of the qvm-filemanager.pl

qvm-filemanager.sh

#!/bin/sh 

set -e

front=$(xprop -notype -root _NET_ACTIVE_WINDOW | awk '{if (match($0,"^_NET_ACTIVE_WINDOW: window id # (0x[0-9a-f]*), 0x0$",m)){print m[1];} exit 0;}' )
test -n "$front"

vm=$(xprop -id "$front" -notype _QUBES_VMNAME | awk '{if (match($0,"^_QUBES_VMNAME = \"([^\"]*)\"$",m)){print m[1];} exit 0;}')

if [ -n "$vm" ]; then
	exec qvm-run -- "$vm" 'sh -c "[ -f /usr/bin/nemo ] && exec /usr/bin/nemo || [ -f /usr/bin/nautilus ] && exec /usr/bin/nautilus --new-window --no-default-window || [ -f /usr/bin/dolphin ] && exec /usr/bin/dolphin"'	
else
	exec /usr/bin/thunar
fi

Considers not installed file managers in templates.