Linux 如何在c中实现计时器？
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How to implement a timer in c?
提问by Sowmya Msk
We want to add a timer to our C program under Linux platform.
我们想在Linux平台下为我们的C程序添加一个定时器。
We are trying to send the packets and we want to find out how many packets get sent in 1 minute. We want the timer to run at the same time as the whileloop for sending the packet is being executed. For example:
我们正在尝试发送数据包，我们想知道 1 分钟内发送了多少数据包。我们希望计时器在执行while发送数据包的循环的同时运行。例如：
while(1)
{
send packets;
}
This loop will keep on sending the packets until ctrl-z is pressed. The timer should be used to stop the loop after 60 seconds.
这个循环将继续发送数据包，直到按下 ctrl-z。应使用计时器在 60 秒后停止循环。
回答by elcuco
man 3 sleep:
男人3睡觉：
NAME sleep - Sleep for the specified number of seconds
SYNOPSIS #include < unistd.h >
unsigned int sleep(unsigned int seconds);
NAME sleep - 休眠指定秒数
概要 #include < unistd.h >
unsigned int sleep(unsigned int seconds);
回答by Fred
Can also check this http://www.gnu.org/software/libc/manual/html_node/Setting-an-Alarm.htmlto set timers which will send signals to your process and you can stop the while loop.
也可以检查这个http://www.gnu.org/software/libc/manual/html_node/Setting-an-Alarm.html来设置将向您的进程发送信号的计时器，您可以停止 while 循环。
回答by JeremyP
Just check the time on every iteration of the loop and when 1 minute has elapsed, count how many packets you have sent.
只需检查循环每次迭代的时间，当 1 分钟过去后，计算您发送的数据包数量。
Editchanged to reflect what the question actually asks!
编辑已更改以反映问题实际提出的问题！
time_t startTime = time(); // return current time in seconds
int numPackets = 0;
while (time() - startTime < 60)
{
send packet
numPackets++;
}
printf("Sent %d packets\n", numPackets);
回答by Lance Richardson
You could do something like this:
你可以这样做：
#include <signal.h>
#include <unistd.h>
#include <stdio.h>
volatile int stop=0;
void sigalrm_handler( int sig )
{
stop = 1;
}
int main(int argc, char **argv)
{
struct sigaction sact;
int num_sent = 0;
sigemptyset(&sact.sa_mask);
sact.sa_flags = 0;
sact.sa_handler = sigalrm_handler;
sigaction(SIGALRM, &sact, NULL);
alarm(60); /* Request SIGALRM in 60 seconds */
while (!stop) {
send_a_packet();
num_sent++;
}
printf("sent %d packets\n", num_sent);
exit(0);
}
If loop overhead turns out to be excessive, you could amortize the overhead by sending N packets per iteration and incrementing the count by N each iteration.
如果循环开销过大，您可以通过每次迭代发送 N 个数据包并在每次迭代中将计数增加 N 来分摊开销。
回答by HuntM
Here is code snippet of itimer that can be used for different time intervals on C with linux platform:
以下是可以在 Linux 平台上的 C 上用于不同时间间隔的计时器的代码片段：
#include <signal.h>
#include <stdio.h>
#include <string.h>
#include <sys/time.h>
void timer_handler (int signum)
{
static int count = 0;
printf ("timer expired %d times\n", ++count);
}
int main ()
{
struct sigaction sa;
struct itimerval timer;
/* Install timer_handler as the signal handler for SIGVTALRM. */
memset (&sa, 0, sizeof (sa));
sa.sa_handler = &timer_handler;
sigaction (SIGVTALRM, &sa, NULL);
/* Configure the timer to expire after 1 sec... */
timer.it_value.tv_sec = 1;
timer.it_value.tv_usec = 0;
/* ... and every 1000 msec after that. */
timer.it_interval.tv_sec = 1;
timer.it_interval.tv_usec = 0;
/* Start a virtual timer. It counts down whenever this process is
* executing. */
setitimer (ITIMER_VIRTUAL, &timer, NULL);
/* Do busy work. */
while (1);
sleep(1);
}
hope it will help.
希望它会有所帮助。
回答by Abhishek Sagar
Use wheetimer (and its variant) data structures to implement timers.
使用 wheetimer（及其变体）数据结构来实现计时器。
