signals

问题 #include <stdio.h> #include <signal.h> void f( int ); int main () { int i ; signal ( SIGINT , f) ; for (i =0; i <5; i ++) { printf ( " hello \n " ) ; sleep (10) ; } } void f( int signum ){ //signal ( SIGINT , f) ; printf ( " OUCH !\n ") ; } I am try to learn handle signals in c. In code above i could not understand the way that function signal works. I understand that when i execute this code when i press control-c function f will be executed and would interrupt the loop.But when i press

问题 this has been bugging me all day. When a program sets itself up to call a function when it receives a certain interrupt, I know that the registers are pushed onto the stack when the program is interrupted, but what I can't figure out is: how do the registers get off the stack? I know that the compiler doesn't know if the function is an interrupt handler, and it can't know how many arguments the interrupt gave to the function. So how on earth does it get the registers off? 回答1: It depends on

问题 I have a problem using sigaction in C++ with this class: class SerialHandler{ private: ... /* Action Handling */ struct sigaction receive_handler; /* Called using the receive_handler*/ static void receive_function(int status); /* Get byte from the Serial Port */ unsigned char receive_byte(); /* Buffer for Singalinterrupt on Reciving */ std::vector<char> in_char_buffer; ... }; I really need to use an Interrupt and really need to use a member function (receive_function) on the Interrupt

问题 I know how a process can respond to signals that were sent to it specifically (e.g. SIGINT , SIGTERM , SIGUSR2 , etc.). But can a process be notified of signals that were sent to a different process? 回答1: Not in standard Unix or POSIX, you cannot be notified for signals sent to another process. See signal(7) and signal-safety(7). However, waitpid(2) and friends can tell you if a child process has terminated with a signal. And killpg(2) sends a signal to a process group (and kill(2) does also

问题 I am trying to catch user key press Ctrl+d on a GUI window to quit. My code looks like this: static gboolean callback(GtkWidget *widget, GdkEventKey *event, gpointer data) { if(event->state == GDK_CONTROL_MASK && event->keyval == 'd') gtk_main_quit(); return FASLE; } This works on my laptop(Ubuntu 11.04, gcc 4.5.2, libgtk 2.24.4). But when I do the same thing on a newer system(Ubuntu 12.10, gcc 4.7.2, libgtk 2.24.13), it doesn't work. I added g_print("%u\n", event->state); before the if

问题 I need to manipulate data from a Django model after its saving, but I also need to access the ManyToManyField. Here's what I want to do: class Lab(Model): institute = ManyToManyField(Institute) def post_save_lab(sender, instance, created, *args, **kwargs): if not instance.institute.all(): # Data processing... post_save.connect(post_save_lab, sender=Lab) The problem is, instance.institute.all() is always empty at that moment... How can I know if the lab has or has not institute? I specify that

问题 This question already has answers here : What does the Q_OBJECT macro do? Why do all Qt objects need this macro? (6 answers) Closed 5 years ago . I am trying to connect a signal to a slot. The project compiles fine, but at runtime I get this error: QObject::connect: No such slot QHeaderView::onFilterAdded(int) here is my code: class MySortFilterProxyModel: public QSortFilterProxyModel { Q_OBJECT public: explicit MySortFilterProxyModel(QObject *parent = 0); ~MySortFilterProxyModel(); void

问题 I got a Question on digital signal processing. Is h(n)= (2 n+5)u(n) memory-less? I think that the because of u(n) , the system is memory-less. Am I right? 回答1: The short answer: No, assuming the provided h(n) represents the usual system impulse response. A memoryless system is characterized with outputs that do not depend on past inputs (and commonly also do not depend on future input). In terms of the impulse response it means that the response h(n) at a time n>0 should not depend on the

问题 Here i have defined a model to create a feed instance in 'models.py': class StreamItem(models.Model): content_type = models.ForeignKey(ContentType) object_id = models.PositiveIntegerField() pub_date = models.DateTimeField() content_object = generic.GenericForeignKey('content_type', 'object_id') def get_rendered_html(self): template_name = 'streams/stream_item_%s.html' % (self.content_type.name) return render_to_string(template_name, { 'object': self.content_object }) def create_stream_item

问题 I'm trying to create a daemon process that handles several child threads. But the child thread doesn't seem to send the signal back to the parent to call the function. i have tried to take it out of the class and make it a standard function but that doesn't seem to help either. class Daemon { public function __construct() { $set = pcntl_signal(SIGCHLD, array($this, 'childSignalHandler')); $pid = pcntl_fork(); if ($pid == -1) { echo 'could not fork'; } elseif ($pid) { // parent sleep(20); //