I'm responsible for a couple of scripts at work, which have used a trap
on CHLD to do some naive parallelisation, starting a new child process
when an existing one ends.
However, when run under bash 4.3.30, all CHLD traps run at the same
time, so my script runs in chunks, rather than keeping a given amount of
processes running at all times. I've been told I can rewrite it using
wait -n instead, but I'm wondering if this is classified as a bug, or if
it's intended to be that way going forwards.
Here's a quick example of what happens (from shbot in #bash on freenode):
43# bash -c "echo \$BASH_VERSION; set -m; trap 'date' CHLD; sleep 1 &
sleep 3"
4.3.30(1)-release
[1]+ Done sleep 1
Wed Jan 14 10:58:33 UTC 2015
Wed Jan 14 10:58:33 UTC 2015
42# bash -c "echo \$BASH_VERSION; set -m; trap 'date' CHLD; sleep 1 &
sleep 3"
4.2.53(1)-release
Wed Jan 14 10:58:36 UTC 2015
Wed Jan 14 10:58:38 UTC 2015
[1]+ Done sleep 1
