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Possible bash bug?

From: John Lawlor
Subject: Possible bash bug?
Date: Wed, 22 Jun 2016 10:34:59 +0100



I came across some unusual behaviour in bash using the ‘-c’ parameter.


If I do the following:


bash -c "ping > $HOME/console.log"  &


This starts two processes bash and ping:


john     18038 17951  0 09:26 pts/14   00:00:00 bash -c ping > /home/john/console.log

john     18039 18038  0 09:26 pts/14   00:00:00 ping


From the process hierarchy bash is the parent process of ping.


Now if I kill bash:


kill -15 18038


And check the process tree again:



john     17951 30467  0 09:25 pts/14   00:00:00 /bin/bash

john     18039     1  0 09:26 pts/14   00:00:00 ping

john     18064 17951  0 09:30 pts/14   00:00:00 ps -f

[1]+  Terminated              bash -c "ping > $HOME/console.log"


Bash is killed but not the child ping process. I was expecting that to be killed also.


If I repeat the exact same steps with ksh –c, it does kill the ping process.


It looks like bash does a double fork or something whereas ksh does only an execute without fork.




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