catch exit status of daemon

catch exit status of daemon

[Yash Jain]

Hello All,
I have one dumb question,
I wanted to write a process which monitors the exit status of the daemon,

The Main process would fork a service, which would internally fork a child
and , exit from the process. If main process wants to query the status of
the daemon, how it can be achived.

For ex :
Process A would call a syslog service, which would internally fork a child,
daemon it and exit, so if process A wants to wait for the syslog process,
is it possible.

Thanks in advance

Regards,
Yash.
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catch exit status of daemon

[nick]

Yash,
There are two ways to do this either use the signals API or IPC(inter-process communication)
libraries. I don't known the functions off the top of my head but this can get you started.
Nick

On 2015-01-06 10:22 AM, Yash Jain wrote:
> Hello All,
> I have one dumb question,
> I wanted to write a process which monitors the exit status of the daemon,
> 
> The Main process would fork a service, which would internally fork a child
> and , exit from the process. If main process wants to query the status of
> the daemon, how it can be achived.
> 
> For ex :
> Process A would call a syslog service, which would internally fork a child,
> daemon it and exit, so if process A wants to wait for the syslog process,
> is it possible.
> 
> Thanks in advance
> 
> Regards,
> Yash.
> 
> 
> 
> _______________________________________________
> Kernelnewbies mailing list
> Kernelnewbies at kernelnewbies.org
> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
> 

catch exit status of daemon

[Valdis.Kletnieks at vt.edu]

On Tue, 06 Jan 2015 20:52:02 +0530, Yash Jain said:

> Process A would call a syslog service, which would internally fork a child,
> daemon it and exit, so if process A wants to wait for the syslog process,
> is it possible.

% man 2 wait
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catch exit status of daemon

[Anuz Pratap Singh Tomar]

On Tue, Jan 6, 2015 at 3:22 PM, Yash Jain <yash2learn@gmail.com> wrote:

> Hello All,
> I have one dumb question,
> I wanted to write a process which monitors the exit status of the daemon,
>
> The Main process would fork a service, which would internally fork a child
> and , exit from the process. If main process wants to query the status of
> the daemon, how it can be achived.
>
> For ex :
> Process A would call a syslog service, which would internally fork a
> child, daemon it and exit, so if process A wants to wait for the syslog
> process, is it possible.
>
> waitpid()
signal()

> Thanks in advance
>
> Regards,
> Yash.
>
> _______________________________________________
> Kernelnewbies mailing list
> Kernelnewbies at kernelnewbies.org
> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
>
>


-- 
Thank you
Warm Regards
Anuz
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catch exit status of daemon

[Nizam Haider]

Anuz Pratap Singh Tomar <chambilkethakur <at> gmail.com> writes:

> 
> 
> 
> On Tue, Jan 6, 2015 at 3:22 PM, Yash Jain <yash2learn <at> gmail.com> 
wrote:Hello All,I have one dumb question,
> I wanted to write a process which monitors the exit status of the daemon,
> 
> The Main process would fork a service, which would internally fork a child 
and , exit from the process. If main process wants to query the status of 
the daemon, how it can be achived.
> 
> For ex :
> Process A would call a syslog service, which would internally fork a 
child, daemon it and exit, so if process A wants to wait for the syslog 
process, is it possible.
> 
> 
> waitpid()
> 
> signal() 
WIFEXITED
WEXITSTATUS
> 
> 
> 
> Thanks in advance
> 
> Regards,
> Yash.
> 
> _______________________________________________
> Kernelnewbies mailing listKernelnewbies <at> 
kernelnewbies.orghttp://lists.kernelnewbies.org/mailman/listinfo/kernelnewbi
es
> 
> 
> -- Thank you Warm RegardsAnuz
> 
> 
> 
> 
> _______________________________________________
> Kernelnewbies mailing list
> Kernelnewbies <at> kernelnewbies.org
> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
> 

catch exit status of daemon

[Sudip Mukherjee]

On Wed, Jan 7, 2015 at 12:57 AM, Nizam Haider <nizamhaider786@gmail.com> wrote:
> Anuz Pratap Singh Tomar <chambilkethakur <at> gmail.com> writes:
>
>>
>>
>>
>> On Tue, Jan 6, 2015 at 3:22 PM, Yash Jain <yash2learn <at> gmail.com>
> wrote:Hello All,I have one dumb question,
>> I wanted to write a process which monitors the exit status of the daemon,
>>
>> The Main process would fork a service, which would internally fork a child
> and , exit from the process. If main process wants to query the status of
> the daemon, how it can be achived.
>>
>> For ex :
>> Process A would call a syslog service, which would internally fork a
> child, daemon it and exit, so if process A wants to wait for the syslog
> process, is it possible.
>>
>>
>> waitpid()
>>
>> signal()
> WIFEXITED
> WEXITSTATUS

doubt --
wait and waitpid will be for the parent process to wait for its child.
but for a daemon the parent is init .
so the exit status should be sent to init and not to his process. then
how does he get the exit status

sudip

>>

catch exit status of daemon

[Yash Jain]

wait and waitpid would not work because a Process A would wait for process
B(which is a parent of the daemon), process B immediately exits and process
A would be notified.
In my case, I want to query the status of process C(which is child of
process B) / grandchild of process A which is a child of init after process
B terminates,

                  fork                            fork
process A -------------> Process B --------------> Process C

Process A should query the status of process C

Once process C is daemon, Process C would be the the child of init.

Can we do something by making a process A to be a daemon (child of init),
because process A and process C are sibling, can siblings query the status
of each other.

IPC is not an option for me, because there are several service and process
A do not know how and what is the process C, it should just monitor so many
child process.

Regards,
Yash.

On Wed, Jan 7, 2015 at 1:35 PM, Sudip Mukherjee <sudipm.mukherjee@gmail.com>
wrote:

> On Wed, Jan 7, 2015 at 12:57 AM, Nizam Haider <nizamhaider786@gmail.com>
> wrote:
> > Anuz Pratap Singh Tomar <chambilkethakur <at> gmail.com> writes:
> >
> >>
> >>
> >>
> >> On Tue, Jan 6, 2015 at 3:22 PM, Yash Jain <yash2learn <at> gmail.com>
> > wrote:Hello All,I have one dumb question,
> >> I wanted to write a process which monitors the exit status of the
> daemon,
> >>
> >> The Main process would fork a service, which would internally fork a
> child
> > and , exit from the process. If main process wants to query the status of
> > the daemon, how it can be achived.
> >>
> >> For ex :
> >> Process A would call a syslog service, which would internally fork a
> > child, daemon it and exit, so if process A wants to wait for the syslog
> > process, is it possible.
> >>
> >>
> >> waitpid()
> >>
> >> signal()
> > WIFEXITED
> > WEXITSTATUS
>
> doubt --
> wait and waitpid will be for the parent process to wait for its child.
> but for a daemon the parent is init .
> so the exit status should be sent to init and not to his process. then
> how does he get the exit status
>
> sudip
>
> >>
>
> _______________________________________________
> Kernelnewbies mailing list
> Kernelnewbies at kernelnewbies.org
> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
>
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catch exit status of daemon

[Bernd Petrovitsch]

On Mit, 2015-01-07 at 14:40 +0530, Yash Jain wrote:
> wait and waitpid would not work because a Process A would wait for process
> B(which is a parent of the daemon), process B immediately exits and process
> A would be notified.
> In my case, I want to query the status of process C(which is child of

> process B) / grandchild of process A which is a child of init after process
> B terminates,

And exactly here ends the usual Unix story because when "Process C" is a
child of `init` (or whatever process has pid 1), "Process A" shouldn't
receive a SIGCLD (because that is delivered only to it's parent process
and one of the main purposes of daemonizing "Process C" is to get to
into that position;-).

>                   fork                            fork
> process A -------------> Process B --------------> Process C
> 
> Process A should query the status of process C
> 
> Once process C is daemon, Process C would be the the child of init.
> 
> Can we do something by making a process A to be a daemon (child of init),
> because process A and process C are sibling, can siblings query the status
> of each other.

Not with the usual model as outlined above.

The short term solution are
- to implement it in the daemons/program/applications.
- to start the daemon in some "debug mode" so that it doesn't daemonize
  itself.
- (if you can't that or won't fix the daemon) to hack init so that when
  some PID terminates, it notifies the other process.

There were patches on LKML so that any process can choose to inherit
daemonized processes forked by (it's own;-) child processes (instead of
'init' - the main reason being the typical desktop manager (kdn, gdm,
xdm, ....) process which also may want to do that) but I don't know the
state of them ....

[ crap deleted ]

Kind regards,
	Bernd
-- 
"I dislike type abstraction if it has no real reason. And saving
on typing is not a good reason - if your typing speed is the main
issue when you're coding, you're doing something seriously wrong."
    - Linus Torvalds