setitimer函数使用笔记
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setitimer函数使用笔记
函数原型int setitimer(int which, const struct itimerval *value,
struct itimerval *ovalue);
DESCRIPTION
The system provides each process with three interval timers, each decrementing in a distinct time domain. When any timer expires, a
signal is sent to the process, and the timer (potentially) restarts.
ITIMER_REAL decrements in real time, and delivers SIGALRM upon expiration.
ITIMER_VIRTUAL decrements only when the process is executing, and delivers SIGVTALRM upon expiration.
ITIMER_PROF decrements both when the process executes and when the system is executing on behalf of the process. Coupled with
ITIMER_VIRTUAL, this timer is usually used to profile the time spent by the application in user and kernel space. SIG-
PROF is delivered upon expiration.
Timer values are defined by the following structures:
struct itimerval {
struct timeval it_interval; /* next value */
struct timeval it_value; /* current value */
};
struct timeval {
long tv_sec; /* seconds */
long tv_usec; /* microseconds */
};
#include < unistd.h >
#include < signal.h >
#include < string .h >
#include < sys / time.h >
#include < errno.h >
void PrintMsg( int Num)
{
printf( " %s\n " , " Hello World " );
return ;
}
int main( int argc, char * argv[])
{
signal(SIGALRM, PrintMsg);
struct itimerval tick;
tick.it_value.tv_sec = 10 ; // 十秒钟后将启动定时器
tick.it_value.tv_usec = 0 ;
tick.it_interval.tv_sec = 1 ; // 定时器启动后，每隔1秒将执行相应的函数
tick.it_interval.tv_usec = 0 ;
// setitimer将触发SIGALRM信号
int ret = setitimer(ITIMER_REAL, & tick, NULL);
if ( ret != 0 )
{
printf( " Set timer error. %s \n " , strerror(errno) );
return - 1 ;
}
printf( " Wait!\n " );
getchar();
return 0 ;
}
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