uscheduleruntimelimit starts CHILD and sends it a TERM
signal after the LIMIT has been reached. 5 seconds later a KILL
signal is sent.
uscheduleruntimelimit exits as soon as the CHILD exits,
preserving its exit code.
LIMIT is given as number and by default interpreted as seconds. To
change its meaning to minutes (or hours, days) append a m (or
h, d) character.
command for this.