C unix: sending a signal to a process with kill isn't the same that from keybord..why?

Question

So I have this parent process A which forks and creates some processes, B and C. C itself will create more, but I don't think it matters.

A forks:

char *argv_exec[] = {
    "/usr/bin/xfce4-terminal",
    "--geometry",
    "160x48",
    "-x",
    "./tv",
    NULL };

pid_tv = fork();

if (pid_tv == 0)
{   
    (void) execv(argv_exec[0], argv_exec);
    fprintf (stderr, "Errore nella execv.\n%s\n",
    strerror(errno) );
    anelito(0);
}

While they all run together, I want to be able to send a signal from process B to its parent process A to make him do something - in this case kill all children and re-fork.

Process A sends its pid to process B in a message.

Parent A handles the signal:

if(signal(SIGQUIT,riparti)==SIG_ERR)
    ...
    void riparti(int s)
    { 
               kill_all_children();
               fork_all_children_again();
    }

Process B sends a SIGQUIT to A when it receives one (it bounces it) process B has:

signal(SIGQUIT,riparti);

void riparti(int a)
    {
          kill(pid_parent,SIGQUIT);
    }

Now when i press CTRL+\ on the window of process B once, all goes well. If i do it a second time, process A does not seem to receive the signal anymore.

It's strange, I can send a SIGQUIT with Ctrl+\\ both from the child window and from the actual parent window (as I'd expect) but once I've done so once the other Ctrl+\\ I press do not seem to work anymore; the character ^\\ is printed on screen but nothing happens. I've also checked with sigpending() and no signal is sent after the first one! — sowdust, Sep 05 '13 at 09:49

score 1 · Accepted Answer · answered Sep 05 '13 at 01:03

1

I think you're killing the parent process from outside the fork code, you're actually sending that signal from process A, which in turn will kill the parent terminal.

answered Sep 05 '13 at 01:03

OneOfOne

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yes thanks! True, the actual command I was calling is /usr/bin/xfce4-terminal which in turn calls the program... however now that i pass the parent (A) pid into a message, I can only use the signal once. I'll edit the main message with more details – sowdust Sep 05 '13 at 01:21

C unix: sending a signal to a process with kill isn't the same that from keybord..why?

1 Answers1