#include <signal.h>#include <sys/types.h>#include <unistd.h>int num;void sig_handle(int signum){	int tmp;	tmp=num;	num=999;	printf("signal number %d\n",signum);	num=tmp;}int main(int argc,char *argv[]){	pid_t child;	signal(SIGUSR1,sig_handle);	child=fork();	if (child==0)	{		while(1)		{			sleep(1);			num++;			printf("number is %d\n",num);			}		exit(1);	}	printf("read send signal!\n");	sleep(5);	kill(child,SIGUSR1);	sleep(2);	printf("sssssss\n");	return 0;}