Hi,

is there a way to catch system signal of "kill" command or "shutdown"?

PS: are there some other ways also to send signals to running a D application?

On Saturday, 5 November 2016 at 02:24:00 UTC, Konstantin Kutsevalov wrote:
> Hi,
>
> is there a way to catch system signal of "kill" command or "shutdown"?
>
> PS: are there some other ways also to send signals to running a D application?

have a look in std.process

I don't think you can catch kill.

On Saturday, 5 November 2016 at 02:24:00 UTC, Konstantin Kutsevalov wrote:
> Hi,
>
> is there a way to catch system signal of "kill" command or "shutdown"?

During the Run-time:
====================

You can register a signal callback, like in this sample (hit CTRL+C once running in a terminal):

import std.stdio;
import core.sys.posix.signal;

bool doQuit;

extern(C) void handler(int num) nothrow @nogc @system
{
    printf("Caught signal %d\n",num);
    doQuit = true;
}

void main(string[] args)
{
    signal(SIGINT, &handler);
    while(true)
    {
        import core.thread;
        Thread.sleep(dur!"msecs"(50));
        if (doQuit)
            break;
    }
}


After termination:
==================

if (tryWait(PID)[0] == true) then the value carried by tryWait(PID)[1] will tell you if the process has exited because of a signal whatever it's, e.g SIGKILL, SIGTERM, SIGINT, ...

On Saturday, 5 November 2016 at 06:17:51 UTC, Basile B. wrote:
> On Saturday, 5 November 2016 at 02:24:00 UTC, Konstantin Kutsevalov wrote:
>> Hi,
>>
>> is there a way to catch system signal of "kill" command or "shutdown"?
>
> During the Run-time:
> ====================
>
> You can register a signal callback, like in this sample (hit CTRL+C once running in a terminal):
>
> import std.stdio;
> import core.sys.posix.signal;
>
> bool doQuit;
>
> extern(C) void handler(int num) nothrow @nogc @system
> {
>     printf("Caught signal %d\n",num);
>     doQuit = true;
> }
>
> void main(string[] args)
> {
>     signal(SIGINT, &handler);
>     while(true)
>     {
>         import core.thread;
>         Thread.sleep(dur!"msecs"(50));
>         if (doQuit)
>             break;
>     }
> }
>
>
> After termination:
> ==================
>
> if (tryWait(PID)[0] == true) then the value carried by tryWait(PID)[1] will tell you if the process has exited because of a signal whatever it's, e.g SIGKILL, SIGTERM, SIGINT, ...

3rd option, from my Windows times I remember that people tend to use launchers
to handle the real application, i.e a process that launches the main process. Then the launcher can have a thread that checks the PID (like in "After Term..."). If SIGKILL isn't handled by a signal() callback then this could be an option.

Do you have to check if a server crashes or something like that ?

On Saturday, 5 November 2016 at 07:52:53 UTC, Basile B. wrote:
> On Saturday, 5 November 2016 at 06:17:51 UTC, Basile B. wrote:
> 3rd option, from my Windows times I remember that people tend to use launchers
> to handle the real application, i.e a process that launches the main process. Then the launcher can have a thread that checks the PID (like in "After Term..."). If SIGKILL isn't handled by a signal() callback then this could be an option.
>
> Do you have to check if a server crashes or something like that ?

not a system crash. just a signal of sistems shutdown or process kill.

On Sunday, 6 November 2016 at 16:05:44 UTC, Konstantin Kutsevalov wrote:
> On Saturday, 5 November 2016 at 07:52:53 UTC, Basile B. wrote:
>> On Saturday, 5 November 2016 at 06:17:51 UTC, Basile B. wrote:
>> 3rd option, from my Windows times I remember that people tend to use launchers
>> to handle the real application, i.e a process that launches the main process. Then the launcher can have a thread that checks the PID (like in "After Term..."). If SIGKILL isn't handled by a signal() callback then this could be an option.
>>
>> Do you have to check if a server crashes or something like that ?
>
> not a system crash. just a signal of sistems shutdown or process kill.

*of system

On Saturday, 5 November 2016 at 06:17:51 UTC, Basile B. wrote:
> On Saturday, 5 November 2016 at 02:24:00 UTC, Konstantin Kutsevalov wrote:
>> Hi,
>>
>> is there a way to catch system signal of "kill" command or "shutdown"?
>
> During the Run-time:
> ====================
>
> You can register a signal callback, like in this sample (hit CTRL+C once running in a terminal):
>
>
> After termination:
> ==================
>
> if (tryWait(PID)[0] == true) then the value carried by tryWait(PID)[1] will tell you if the process has exited because of a signal whatever it's, e.g SIGKILL, SIGTERM, SIGINT, ...

Thank you!

On 11/6/16 11:05 AM, Konstantin Kutsevalov wrote:
> On Saturday, 5 November 2016 at 07:52:53 UTC, Basile B. wrote:
>> On Saturday, 5 November 2016 at 06:17:51 UTC, Basile B. wrote:
>> 3rd option, from my Windows times I remember that people tend to use
>> launchers
>> to handle the real application, i.e a process that launches the main
>> process. Then the launcher can have a thread that checks the PID (like
>> in "After Term..."). If SIGKILL isn't handled by a signal() callback
>> then this could be an option.
>>
>> Do you have to check if a server crashes or something like that ?
>
> not a system crash. just a signal of sistems shutdown or process kill.

You can catch signals, but some the OS does not let you catch.

IIRC, Posix systems on shutdown first send a "TERM" signal (15) which is the default signal for the kill command line as well. If the process does not clean up within a certain timeout, then it is sent the "KILL" signal (9), which CANNOT be caught.

What you want is to handle process cleanup on the TERM signal.

-Steve