C语言 如何触发 SIGUSR1 和 SIGUSR2？
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How to trigger SIGUSR1 and SIGUSR2?
提问by haunted85
I'm getting acquainted with signals in C. I can't figure out what kind of signals SIGUSR1and SIGUSR2are and how can I trigger them. Can anyone please explain it to me?
我越来越与C.我认识的信号不能想出什么样的信号SIGUSR1，并SIGUSR2是，我怎么能触发它们。任何人都可以向我解释一下吗？
回答by Oliver Charlesworth
They are user-definedsignals, so they aren't triggered by any particular action. You can explicitly send them programmatically:
它们是用户定义的信号，因此它们不会由任何特定操作触发。您可以以编程方式显式发送它们：
#include <signal.h>
kill(pid, SIGUSR1);
where pidis the process id of the receiving process. At the receiving end, you can register a signal handler for them:
哪里pid是接收进程的进程ID。在接收端，您可以为它们注册一个信号处理程序：
#include <signal.h>
void my_handler(int signum)
{
if (signum == SIGUSR1)
{
printf("Received SIGUSR1!\n");
}
}
signal(SIGUSR1, my_handler);
回答by cnicutar
They are signals that application developers use. The kernel shouldn't ever send these to a process. You can send them using kill(2)or using the utility kill(1).
它们是应用程序开发人员使用的信号。内核不应该将这些发送到进程。您可以使用kill(2)或使用该实用程序发送它们kill(1)。
If you intend to use signals for synchronization you might want to check real-time signals (there's more of them, they are queued, their delivery order is guaranteed etc).
如果您打算使用信号进行同步，您可能需要检查实时信号（它们更多，它们已排队，它们的交付顺序得到保证等）。
回答by Евгений Кашинский
terminal 1
1号航站楼
dd if=/dev/sda of=debian.img
terminal 2
2号航站楼
killall -SIGUSR1 dd
go back to terminal 1
回到1号航站楼
34292201+0 records in
34292200+0 records out
17557606400 bytes (18 GB) copied, 1034.7 s, 17.0 MB/s
