Question

哪些函数会产生sigalrm信号

Answer 1

signal(SIGALRM, alarmhandle); 表示给当前进程注册SIGALRM信号处理代码，如果收到SIGALRM信号，就会去执行alarmhandle函数<pre t="code" l="bash">$ man signal

SYNOPSIS
#include <signal.h>
typedef void (*sighandler_t)(int);
sighandler_t signal(int signum, sighandler_t handler);
DESCRIPTION
The signal() system call installs a new signal handler for the signal with number signum. The signal handler is set to sighandler which may be a user specified function, or either SIG_IGN or SIG_DFL.
signal()函数是个系统调用，该函数按signum设定一个新的信号处理句柄（函数）.新设定的处理函数可以是用户自定义的函数，也可以是系统指定的SIG_IGN 或 SIG_DFL.参考代码：
<pre t="code" l="cpp">#include <signal.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
void alarmhandle(int sig)
{
printf("recv sig:%d\n", sig );
printf("exit!\n");
exit(0);
}
int main()
{
signal( SIGALRM, alarmhandle );
printf("begin\n");
alarm(5); //定时器，用于在5秒后产生SIGALRM信号
while( 1 );
return 0;
}运行结果：beginrecv sig:14exit!