Re: [Help-bash] Killing subshells

[Bob Proulx]

Paul Wagner wrote:
> Dear bashers,
> 
> I am trying to create a simple script to schedule wget to grab radio
> programmes.  Since I occasionally lose the connection, I ended up with
> something like
...
>     kill %

Jesse has already pointed out that main problem you asked about.
However you are using wget and wget can retry.  It might be a more
robust solution to try the wget options to retry the connection with
shorter timeouts.  Perhaps something like this:

  wget --retry-connrefused --waitretry=10 --read-timeout=30 --timeout=20 -t 0

Also important is to always check the exit code and if you want you
could loop and retry that upon error.  Perhaps something like this:

until wget --retry-connrefused --waitretry=10 --read-timeout=30 --timeout=20 -t 
0 \
     -a "$name.log" -O "$name-$i.mp3" "$url"; do
  sleep 30
done

Of course that loops indefinitely but exiting after a count of loops
is reasonable too.

However if you want to put things into the background then I recommend
always capturing the job id from $! into a variable.  Then set up a
trap handler such that upon exit any background job can be sent the
signal.  Perhaps something like this quickly created snippet:

#!/bin/sh
unset rc
cleanup() {
  test -n "$rc" && kill $rc && unset rc
}
trap "cleanup" EXIT
trap "cleanup; trap - HUP; kill -HUP $$" HUP
trap "cleanup; trap - INT; kill -INT $$" INT
trap "cleanup; trap - QUIT; kill -QUIT $$" QUIT
trap "cleanup; trap - TERM; kill -TERM $$" TERM
sleep 30 &
rc=$!
sleep 10

That way an interrupt with Control-C will also send a kill to the
background task.

Hope that helps!
Bob