Avoid zombie processes with std.process

[FreeSlave via Digitalmars-d]

On Thursday, 25 August 2016 at 14:53:30 UTC, Shachar Shemesh 
wrote:
> On 25/08/16 11:46, FreeSlave wrote:
>> On Thursday, 25 August 2016 at 07:32:29 UTC, Shachar Shemesh 
>> wrote:
>>> On 24/08/16 14:04, FreeSlave wrote:
>>>> Are there plans on adding something like 
>>>> spawnProcessDetached that would
>>>> start processes completely independent from parent? I.e. in 
>>>> other
>>>> process group and, what is important, with no need for wait.
>>>>
>>>> On Posix that could be done via double fork technique. Not 
>>>> sure about
>>>> Windows.
>>>
>>> Double fork on Posix is, usually, used for something slightly
>>> different. In particular, since you bring up the process 
>>> group, I
>>> think you mean daemonization.
>>>
>>> Daemonization, however, does a bit more than create a new 
>>> process
>>> group and double forking.
>>>
>>> http://forum.dlang.org/thread/d83ugn$265f$1@digitaldaemon.com 
>>> has
>>> discussion and some code regarding this issue.
>>>
>>> Shachar
>>
>> It's not about daemonization only. Different process group is 
>> needed to
>> prevent signal distribution. Again, e.g. file manager and 
>> launched
>> application may want to not be connected in any way.
>
> Yes, that's part of daemonization. So is chdir somewhere else 
> and closing all open file descriptors, including stdin/out/err.
>
> http://0pointer.de/public/systemd-man/daemon.html#SysV%20Daemons

It's part of daemonization, but again, I'm not talking 
specifically about daemons. I'm talking about spawning of 
detached process (you may think about it as daemonization, but 
with less/different requirements)

Of course chdir and file descriptors should be configurable.

E.g. file managers usually set working directory of process to 
the path of executable.

When launching usual applications it's better to not close 
standard file descriptors, but redirect them to /dev/null, since 
real closing may break some apps.

Currently spawnProcess allows to set working directory and fds, 
but it implies you call wait afterwards. It would be cool if 
standard library provided the way to spawn process without 
worrying about zombies. And yes, with enough options it could 
provide support for full daemonization too (i.e. including 
closing standard fds).