Re: std.process - POSIX specific callback

[nazriel]

On Thursday, 6 June 2013 at 17:18:20 UTC, Steven Schveighoffer 
wrote:
On Thu, 06 Jun 2013 12:05:14 -0400, nazriel <s...@dzfl.pl> 
wrote:

Would it be possible to add to std.process.Config POSIX 
specific callback which would be called after fork()?

It is currently main blocker in switching dpaste-be from 
handmade process handling module to std.process.

It could look something like this.

struct Config {
     // current fields
     void delegate() posixCallback;
}

// ...

int i = fork();
if (i > 0)
{
//...
   if (config.posixCallback !is null)
        config.posixCallback();
//...
}

Such construct would allow for various child process 
manipulation, for instance
dropping root privileges or setting limits via setrmlimit.

Example:

config.posixCallback = {
    setguid(ourGUID);
    setgroups(ourGROUPS);
    setuid(ourUID);

    setrmlimit(NFORK, 123);
};


AFAIK we already have Windows specific flag related to 
spawning console for GUI apps.

I can make pull request ASAP when I get reasonable name for 
field.

Lars? ;)

I agree with the ability, but not with the interface.  If this 
is to be done, it should be at a lower level, not inside 
config.  Keep in mind that std.process is generalized for both 
Windows and Posix, with very minor differences.

-Steve

I am aware that std.process is generalized but I doubt such 
useful functionality which is usable on various Posixen is more 
disturbing than Windows-only suprpressConsole 
https://github.com/D-Programming-Language/phobos/blob/master/std/process.d#L954

But I was mistaken. Config is an enum not struct, so yeah, not 
worth changing it only for sake of posix callback.

So maybe module level variable?

module std.process;

// ...
void delegate() posixPostFork = null;
// ...


I would *really* love to see this implemented. It is really basic 
stuff for posixen.

Thanks a lot for responding Steven.