直接看代碼

#include <stdio.h>#include <signal.h>typedef void (*signal_handler)(int); //定義函數指針void heart_handler_fun(int signal_num){    alarm(30);//睡眠30S    PRintf("catch signal %d/n", signal_num);}int main(){    printf("start signal/n");    signal_handler p_signal = heart_handler_fun;    signal(SIGALRM, p_signal);    alarm(30);//睡眠30S,觸發signal SIGALRM    while(1);//一定要循環，要不然主線程退出，整個程序就退出了    return 0;}