Created attachment 1478236 [details]
Patch for zombie problem - 1 line.

Description of problem:
Using the 'exec' command in a swatch config file causes zombie processes to be left.

Version-Release number of selected component (if applicable):
swatch-3.2.3-11.el7.noarch

How reproducible:
Relatively easily.

Steps to Reproduce:
1. Install swatch from yum/dnf.
2. cd /tmp and create file 'swatch.conf' with content:
        watchfor /something/
            exec echo "$S_" | mail -s test1 root
3. Start swatch with: swatch --config-file=/tmp/swatch.conf --script-dir=. --daemon --tail-file /var/log/messages >>/tmp/swatch.log
4. Send something to be detected: logger something from me

Actual results:
Checking the root account mail will show the logger message (which is what it should do).
Running 'ps auxww' shows:
=====
root     15529  0.0  0.0      0     0 ?        Z    15:08   0:00 [sh] <defunct>
=====

This zombie wasn't present before. A zombie seems to produced for each exec command. So if the config file has 5 execs in it, then 5 zombies will be produced if each exec is executed.

Expected results:
No zombies to be left behind.

Additional info:

This has been a problem for us for many years. We use swatch with the (previously 'big brother') 'xymon' software so that when a match is found xymon alerts us of the fact (and the match) on its web interface.

The problem seems to have been first reported here:
https://sourceforge.net/p/swatch/bugs/36/

As can be seen I added then that we had the same problem, but that the fix solved it for us. It has done so since then (so for the past several years).

I will add that I have tried contacting the swatch author a couple of times to see if would reassign the project to me, or make me co-author. I have heard nothing though. I gather that others have tried too, with no luck. I still find swatch the best at what it does, and it integrates so well with xymon that it is a shame that it appears to be dead.