[Gambas-user] Starting a Process and forgetting about it

[Bruce]

On Tue, 2013-08-13 at 12:15 +0200, Tobias Boege wrote:
> On Tue, 13 Aug 2013, Beno?t Minisini wrote:
> > > However, I don't think this is a common enough scenario to have it
> > > implemented directly in the Process object. I got by by using Shell
> > > "setsid ... &". Whereas automatically killing background child processes
> > > seems to be a nice addition. Thanks for your effort anyway.
> > >
> > > Regards,
> > > Tobi
> > >
> > 
> > I could call setsid() for the child process, but I have no syntax in the 
> > EXEC/SHELL instruction for that. I will think about it...
> > 
> 
> Besides the syntax, there is another thing to be aware of: If there is a
> pipe from child -> parent (write -> read) and after the parent dies, the
> child writes to the pipe, it will receive a SIGPIPE and die, too, if it
> doesnt't catch this signal.
> 
> It means if whatever flag to enable setsid() is set, the user must carefully
> think about adding For Read/Write/Input/Output.
> 
> Regards,
> Tobi

Good morning,

Did this ever get taken further? (Another long post sorry!)

I now find myself in a similar situation to Tobi, a little simpler but
with an added twist.

Basically, we have about 8 projects that can shell each other in a
certain heirarchy.  Each of these provides functionality based on a
"log-in role" matching the role that the user wants to assume for that
session. So a simple example of a hierarchy would be
manager-->analyst-->tester-->testdeveloper.  That is the manager role
can shell the analyst role project which can shell the tester role etc.
There are other more complex heirarchies.

What I need to provide is two exit strategies, "Quit" and "Quit All"
that would nicely close down either the current project leaving any
child processes running or close the current project and all child
processes respectively. The "twist" is that they want the "Quit All" to
also close any parent processes, in other words to work both up and down
the chain at every level. I think these are two different things from
the Gambas point of view (and on further consideration, lets leave that
out of this.)

I thought that the 1) hProc.Ignore=True could provide the "Quit All" for
the first matter, and I think hProc.Ignore=False might provide the
"Quit" but it would leave the parent process running which in turn wont
exit until the remaining child processes exit.  

Here's the issue:
Re 1) Since the user could start multiple child processes I use a global
array $processes of type Process[] and add the hProc every time they
start a new child. The two handlers for the Quit menu items are:

        Public Sub mnuExit_Click()
        
          Me.Close
        
        End
        
        Public Sub ExitAll_Click()
        
          Dim hProc As Process
          
          For Each hProc In $Processes
            $hProc.Ignore = True
          Next
        
          Me.Close
        
        End

When I run this inside the IDE it all works, no matter how many child
processes they kick off. ps f -U bb -o pid,ppid,args shows (abridged
output):
  PID  PPID COMMAND
17447     1 gbr3 /usr/bin/gambas3
18411 17447  \_ /usr/bin/gbx3 -g -f 17447 /.../atestmgr/tmmanager
18439 18411      \_ gbr3 /.../atestmgr/tmttester/tmttester.gambas
18449 18411      \_ gbr3 /.../atestmgr/tmdeveloper/tmdeveloper.gambas
18468 18411      \_ gbr3 /.../atestmgr/tmanalyst/tmanalyst.gambas

and when I "Quit All" from proc 18411 they all close down.

Now if I run the compiled tmmanager from a vterminal I get:
  PID  PPID COMMAND
17187     1 lxterminal
17872 17187  \_ /bin/bash
18722 17872      \_ gbr3 ./tmmanager.gambas
18739 18722          \_gbr3 /.../atestmgr/tmdeveloper/tmdeveloper.gambas
18744 18722          \_ gbr3 /.../atestmgr/tmttester/tmttester.gambas
18751 18722          \_ gbr3 /../atestmgr/tmanalyst/tmanalyst.gambas

as expected, BUT when I "Quit All" (from 18772) the children stay alive:

  PID  PPID COMMAND
18751     1 gbr3 /.../atestmgr/tmanalyst/tmanalyst.gambas
18744     1 gbr3 /.../atestmgr/tmttester/tmttester.gambas
18739     1 gbr3 /.../atestmgr/tmdeveloper/tmdeveloper.gambas
17187     1 lxterminal
17872 17187  \_ /bin/bash

and magically they have moved to the init proc.

Finally, If I just "Quit" from either the IDE debug mode or from the
vterminal the expected occurs - the original process stays alive until
the last child process exits.

So, it appears gbx3 and gbr3 are doing different things?

regards
Bruce