Re: Execute an OS command and capture output

[Victor Porton <porton@narod.ru>]

Dmitry A. Kazakov wrote:

> On 2017-11-13 21:16, Victor Porton wrote:
>> Dmitry A. Kazakov wrote:
>> 
>>> GTK is not Web-based. It is written in C.
>> 
>> I meant that my software (not GTK) is Web based.
> 
> Well, Web-based as browser side or web-based as server side. On the
> server side you can do anything on the browser side basically nothing.

I mean server-based.

If it were browser-based, I would write to a JavaScript group instead of Ada 
group.

>>>> Is it possible to extract this code and use it separately?
>>>
>>> Sources of GLib are freely available.
>>>
>>> But it would be too complicated, especially under Windows were the GLib
>>> implementation uses a helper process.
>> 
>> It seems we need a helper process on Linux/Unix too:
>> 
>>  From https://codelabs.ch/spawn-manager/index.html
>> 
>> The Ada spawn manager implements the concept described in the GNAT GPL
>> package System.OS_Lib. It is used to solve the problem of spawning
>> processes at arbitrary times from multitasking Ada programs:
> 
> I have no idea why spawning a process should be a problem from a task.
> 
>> In your opinion, is it really necessary?
> 
> No idea. It is not necessary under with Win32 API. As for Linux I don't
> know if Posix calls must be done from a dedicated task. I somewhat doubt
> that.

I suspect, you doubt in vain. It is got from a very reputable source 
(SYSTEM.OS_LIB specification from GNAT COMPILER COMPONENTS):

[[
If the parent is using tasking, and needs to spawn subprocesses at 
arbitrary 
times, one technique is for the parent to spawn (very early) a particular 
spawn-manager subprocess whose job is to spawn other processes. The spawn-
manager avoids tasking. The parent sends messages to the spawn-manager 
requesting it to spawn processes, using whatever inter-process 
communication 
mechanism you like, such as sockets.
]]

-- 
Victor Porton - http://portonvictor.org