Linux信号(5) --时间与定时器
三种不同精度的睡眠
1.sleep
#include
unsigned int sleep(unsigned int seconds);
RETURN VALUE
Zero if the requested time has elapsed, or the number of seconds left to sleep, if the call was interrupted by a signal handler.
//保证睡眠5秒
int sleepTime = 5;
do
{
sleepTime = sleep(sleepTime);
}
while (sleepTime > 0);
2.usleep(以微秒为单位)
int usleep(useconds_t usec);
The type useconds_t is an unsigned integer type capable of holding integers in the range [0,1000000].
Programs will be more portable if they never mention this type explicitly.
3.nanosleep(以纳秒为单位)
#include
int nanosleep(const struct timespec *req, struct timespec *rem);
req指定睡眠的时间, rem返回剩余的睡眠时间
struct timespec
{
time_t tv_sec; /* seconds: 秒 */
long tv_nsec; /* nanoseconds: 纳秒 */
};
三种时间结构
time_t //seconds
struct timeval {
long tv_sec; /* seconds */
long tv_usec; /* microseconds 微秒*/
};
struct timespec {
time_t tv_sec; /* seconds */
long tv_nsec; /* nanoseconds */
};
定时器
setitimer 间歇性参数SIGALRM信号
#include
int setitimer(int which, const struct itimerval *value, struct itimerval *ovalue));
setitimer()比alarm功能强大，支持3种类型的定时器
参数
第一个参数which指定定时器类型
第二个参数是请求的时间
第三个参数是定时器原来所关联的值
struct itimerval
{
struct timeval it_interval; /* next value : 产生信号的间隔时间*/
struct timeval it_value; /* current value : 第一次产生信号的时间*/
};
struct timeval {
long tv_sec; /* seconds */
long tv_usec; /* microseconds 微秒*/
};
which值
ITIMER_REAL： 经过指定的时间后，内核将发送SIGALRM信号给本进程 (用的较多)
ITIMER_VIRTUAL ： 程序在用户空间执行指定的时间后，内核将发送SIGVTALRM信号给本进程
ITIMER_PROF ： 进程在内核空间中执行时，时间计数会减少，通常与ITIMER_VIRTUAL共用，代表进程在用户空间与内核空间中运行指定时间后，内核将发送SIGPROF信号给本进程。
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#define ERR_EXIT(m) \
do \
{ \
perror(m); \
exit(EXIT_FAILURE); \
} while(0)
void handler(int sig)
{
printf("recv a sig=%d\n", sig);
}
int main(int argc, char *argv[])
{
if (signal(SIGALRM, handler) == SIG_ERR)
ERR_EXIT("signal error");
struct timeval tv_interval = {1, 0};
struct timeval tv_value = {5, 0};
struct itimerval it;
it.it_interval = tv_interval;
it.it_value = tv_value;
setitimer(ITIMER_REAL, &it, NULL);
for (;;)
pause();
return 0;
}
可以看到第一次发送信号是在5s以后，之后每隔一秒发送一次信号
获得产生时钟信号的剩余时间
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#define ERR_EXIT(m) \
do \
{ \
perror(m); \
exit(EXIT_FAILURE); \
} while(0)
int main(int argc, char *argv[])
{
struct timeval tv_interval = {1, 0};
struct timeval tv_value = {1, 0};
struct itimerval it;
it.it_interval = tv_interval;
it.it_value = tv_value;
setitimer(ITIMER_REAL, &it, NULL);
int i;
for (i=0; i<10000; i++);
//第一种方式获得剩余时间
struct itimerval oit;
setitimer(ITIMER_REAL, &it, &oit);//利用oit获得剩余时间产生时钟信号
printf("%d %d %d %d\n", (int)oit.it_interval.tv_sec, (int)oit.it_interval.tv_usec, (int)oit.it_value.tv_sec, (int)oit.it_value.tv_usec);
//第二种方式获得剩余时间
//getitimer(ITIMER_REAL, &it);
//printf("%d %d %d %d\n", (int)it.it_interval.tv_sec, (int)it.it_interval.tv_usec, (int)it.it_value.tv_sec, (int)it.it_value.tv_usec);
return 0;
}
getitimer无需设置新时钟获取旧的时钟信息