前言

cocoa进程在异常退出的时候经常无法被AppDelegate监测到，于是乎采用一种更为底层的方式监听

#include <sys/event.h>


- (void)listenPid:(NSInteger)processID
{
    //需要将监听放入后台线程
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
        pid_t pid = (pid_t)processID;
        if (pid > 0) {
            int kq=kqueue();
            if (kq == -1) {
                fprintf(stderr,"kqueue returned -1.");
                return ;
            }
            
            struct kevent ke;
            EV_SET(&ke, pid, EVFILT_PROC, EV_ADD, NOTE_EXIT, 0, NULL);
            
            if (kevent(kq, &ke, 1, NULL, 0, NULL)<0) {
                fprintf(stderr,"kevent failed.");
            }
            
            
            for(;;) {
                memset(&ke,0,sizeof(struct kevent));
                if(kevent(kq, NULL, 0, &ke, 1, NULL)<0){
                    fprintf(stderr,"kevent failed.");
                }
                
                if (ke.fflags & NOTE_EXIT) {
                    fprintf(stderr,"app exit.");
                    break;
                }
            }
        }
        
        dispatch_async(dispatch_get_main_queue(), ^{
            //通知进程退出，做退出前的清理工作
        });
    });
}