On 12/29/2008 04:56 PM, 平天韩 wrote:
> 2008/12/30, Jerry Feldman <gaf@xxxxxxx>:
>
>> On 12/29/2008 10:05 AM, 平天韩 wrote:
>>
>>> hi,
>>>
>>> It seems that when I logout from the console, the background process
>>> doesn't get HUP signal:
>>> { trap "echo Ignore HUP >>/tmp/trap.out" 1; while sleep 3;do echo
>>> hello >>/tmp/hello.txt;done; }&
>>> And it seems it will become a daemon and run forever until rebooting.
>>> Is this correct? Why it didn't get HUP signal?
>>>
>>> Thanks!
>>>
>>>
>>>
>> Are you running this from a terminal window?
>>
>
> I am running this in tty2, a console. I just type those into the
> console and run it, then logout.
>
>
>> Are you possibly setting nohup in your environment.
>>
>
> It seems it is. But how?
>
>
>> Are you typing the above commands directly? What happens if you place
>> these into a script and run the script in the background?
>>
>> There are a number of things that can cause a shell script to ignore the
>> HUP signal. I tested this as a script on an Ubuntu laptop, and it
>> behaved the same as yours:
>>
>> The process remained. So the issue is not that exiting the parent
>> process (GNOME Term) or logging out of GNOME fails to issue a HUP, it is
>> that the process itself ignores the HUP signal since I sent a "kill -HUP
>> <pid>" to the process.
>>
>> If you simply send the HUP signal, you will see that "Ignore HUP" will
>> appear in /tmp/trap.out".
>>
>>
> I have the same results with you.
>
>
>> The signal(1) command is probably the culprit, though the man pages are
>> vague.
>>
>>
> I suspect of that maybe the logout doesn't send out HUP to these
> background processes?
>
After looking at this again now that I understand the specific issue. I
would agree.
--
Jerry Feldman <gaf@xxxxxxx>
Boston Linux and Unix
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