C：通过alarm发送信号

可以通过alarm定时发送SIGALRM信号：

#include <unistd.h>
unsigned int alarm(unsigned int seconds);

alarm()函数用来在seconds秒之后安排发送一个SIGALRM信号，如果seconds为0，将取消所有已设置的闹钟请求。alarm()函数的返回值是以前设置的闹钟时间的余留秒数，如果返回失败返回-1。

#include <unistd.h>
#include <sys/types.h>
#include <stdlib.h>
#include <stdio.h>
#include <signal.h>#include <time.h>time_t timeStamp()
{time_t time_now = time(NULL); return time_now;
}static int alarm_done = 0;void handle_alarm(int sig)
{printf("handle alarm ts:%ld\n", timeStamp());alarm_done = 1;
}int main()
{signal(SIGALRM, handle_alarm);printf("set alarm ts:%ld\n", timeStamp());fflush(stdout);alarm(3);pause();if(alarm_done == 1){printf("recv a alarm ts:%ld\n", timeStamp());}return 0;
}

 运行程序输出：

set alarm ts:1691316070
handle alarm ts:1691316073
recv a alarm ts:1691316073