[maemo-developers] Check if application is run

[From: Eero Tamminen]

Hi,

ext Michael Stepanov wrote:
> Thanks for your suggestions. IMHO the most appropriate way (but probably not
> easiest) is to use DBUS functionality as Mika Yrjölä described. What do you
> think?

It depends from whether you're going to use D-BUS for anything else than
launching the application (do you need to listen to system events for
example like all the pre-installed applications) and how much you care
about user not running multiple instances of the application at the same
time (accidentally).

Some SDL programs for example don't use D-BUS (games might have
a Gtk/Hildon UI wrapper for them using D-BUS though).


	- Eero


> On 11/15/07, Eero Tamminen <eero.tamminen at nokia.com> wrote:
>> Hi,
>>
>> ext Aleksandr Koltsoff wrote:
>>> Eero Tamminen wrote:
>>>> ext Aleksandr Koltsoff wrote:
>>>>> I think in your case it would be sufficient to do something like this:
>>>>> while true; do
>>>>>   ./run-your-application params
>>>>>   sleep 2
>>>>> done
>>>>>
>>>>> Or in C:
>>>>>
>>>>> while(1) {
>>>>>   system("./run-your-application params");
>>>>>   sleep(2);
>>>>> }
>>>> That would shorten the battery life. If one really needs/wants
>>>> to kludge things with polling, the interval should be several
>>>> times larger.
>>> When the application is running, both methods wait for the process to
>>> terminate, i.e., no polling. man 3 system. The idea originally was that
>>> should the application terminate, it will be restarted after a while.
>> Sorry, I didn't read your mail properly (need to get new glasses
>> one of these days...), I just saw the "sleep 2".
>>
>>
>>> If the application is completely broken, and will fail to start in any
>>> case, then this would amount to polling, and would shorten battery life.
>> This would happen also if the process daemonizes itself.
>>
>>
>>> My original post did suggest handling exit codes of the child properly,
>>> but I guess that was lost somewhere in the process..
>>>
>>>>> Linux (kernel) does not have a non-polling mechanism to track
>>>>> PID-existance for non-related processes.
>>>> It has, you just need to be the process parent.  :-)
>>> Note the "non-related" part :-). Parent <-> child = related processes.
>>
>>         - Eero
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> 
> 
>