core-agent-linux/qubes-rpc/qubes.WaitForSession

#!/bin/sh

# old API - get the user from caller
#read -r IGNORE_USERNAME

# use default user provided in QubesDB, or hardcoded 'user' - this must be the
# same as the X session owner
USERNAME=$(qubesdb-read /default-user || echo 'user')
cmd='echo $$ >> /tmp/qubes-session-waiter; [ ! -f /tmp/qubes-session-env ] && exec sleep inf'
if [ "$(id -un)" = "$USERNAME" ]; then
    sh -c "$cmd" 2>/dev/null
else
    su -c "$cmd" - "$USERNAME" 2> /dev/null
fi
# the above line is _expected_ to be terminated by a signal, don't treat this as a failure
exit 0