signals

I have a parent process spanning several child processes. I want to know when any child process exits by registering a SIGCHLD signal handler. The question is, what happens if another SIGCHLD (or any other signal) is received, while the parent process is already in a signal handler? I can think of the following outcomes: The signal is ignored The signal is queued, and will be processed as soon as the current handler returns The current handler is in turn interrupted, just like the main program Which one is correct? In your concrete example (the same signal being received), the signal is

I want to use signals and slots in my program, but unfortunately they should be used for transmitting several different data types (e.g. QString, double, etc.) and I don't want to write twenty different slots just because I need one for each data type. But when I want to declare a slot like template <typename t> void Slot1(t data); QT tells me that it is not possible to use templates in signals and slots. Is there a workaround? Or can my approach simply improved? Accurate answer: It is impossible Workaround: You can do something like this with new signals and slots syntax: QSlider *slid = new

In bash script I handle different signal as follows: #!/bin/bash sighdl () { echo "signal caught" #do something exit 0 } trap sighdl SIGKILL SIGINT SIGTERM Above code handle signal properly for following activity: Ctrl + C kill pid pkill scriptname For kill -9 pid it does not call sighdl . As per my understanding (if I am not wrong) kill -9 sends the SIGKILL signal. Any idea? You cannot do that. Yes 9 is SIGKILL and Unix system by design doesn't allow any script/program to trap SIGKILL due to security reasons. Otherwise any script can trap & ignore SIGKILL which will make impossible to

Perhaps you've seen this... 2012-03-07T15:36:25+00:00 heroku[web.1]: Stopping process with SIGTERM 2012-03-07T15:36:36+00:00 heroku[web.1]: Stopping process with SIGKILL 2012-03-07T15:36:36+00:00 heroku[web.1]: Error R12 (Exit timeout) -> Process failed to exit within 10 seconds of SIGTERM 2012-03-07T15:36:38+00:00 heroku[web.1]: Process exited with status 137 This is a well known problem when running unicorn on heroku ... heroku uses SIGTERM for graceful shutdown unicorn uses SIGTERM for quick shutdown Can I tell heroku to send SIGQUIT ? Or can I tell unicorn to treat SIGTERM as graceful

Inside the constructor, there is a connection: connect(&amskspace::on_board_computer_model::self(), SIGNAL(camera_status_changed(const amskspace::camera_status_t&)), this, SLOT(set_camera_status(const amskspace::camera_status_t&))); And the method: void camera_model:: set_camera_status(const amskspace::camera_status_t& status) { disconnect(&amskspace::on_board_computer_model::self(), SIGNAL(camera_status_changed(const amskspace::camera_status_t&)), this, SLOT(set_camera_status(const amskspace::camera_status_t&))); // do the job } And I'd like to disconnect this slot after the first call. The

This is a follow up to my other post Installing signal handler with Python . In short, Linux blocks all signals to PID 1 (including SIGKILL) unless Init has installed a signal handler for a particular signal; as to prevent kernel panic if someone were to send a termination signal to PID1. The issue I've been having, is it would seem that the signal module in Python doesn't install signal handlers in a way the system recognises. My Python Init script was seemingly, completely ignoring all signals as I think they were being blocked. I seem to have found a solution; using ctypes to install the