How to Use setitimer in linux c Programming, linuxsetitimer

How to Use setitimer in linux c Programming, linuxsetitimer

In linux c programming. Setitimer is a function that is frequently used than timer. Latency and timing

Header files to be introduced during use:

#include 
 

Setitimer function prototype:

int setitimer(int which, const struct itimerval *new_value, struct itimerval *old_value);

The which limit number indicates the type. Optional values:

ITIMER_REAL: calculated based on the real time of the system. It sends the SIGALRM signal.

ITIMER_VIRTUAL: calculates the time spent by the process in the user State. It sends the SIGVTALRM signal.

ITIMER_PROF: the time spent by the process in the user and kernel modes. It sends a SIGPROF signal.

The new_value and old_value are the itimerval struct. Let's take a look at the definition of the itimerval struct:

struct itimerval {    struct timeval it_interval; /* next value */    struct timeval it_value;    /* current value */};struct timeval {    time_t      tv_sec;         /* seconds */    suseconds_t tv_usec;        /* microseconds */};

Itimeval is composed of two timeval struct, including TV _sec and TV _usec. The value of TV _se is second. TV _usec is in microseconds (that is, 1/1000000 seconds)

The settimer mechanism is to first Countdown to it_value and trigger a signal when it_value is zero. Then reset to it_interval. Continue to countdown to it_value. Keep repeating like this.

Based on this mechanism. Setitimer can be used for both delayed and scheduled operation.

If it_value is 0, the signal will not be triggered, so the it_value must be greater than 0. If it_interval is zero, only the delay will occur. Not scheduled (that is, only one signal is triggered ).

Old_value limit, which is frequently unavailable. Set to NULL, which is used to store the new_value value set during the last setitimer call.

Example:

#include 
 
  #include 
  
   #include 
   
    void signalHandler(int signo){    switch (signo){        case SIGALRM:            printf("Caught the SIGALRM signal!\n");            break;   }}int main(int argc, char *argv[]){    signal(SIGALRM, signalHandler);    struct itimerval new_value, old_value;    new_value.it_value.tv_sec = 0;    new_value.it_value.tv_usec = 1;    new_value.it_interval.tv_sec = 0;    new_value.it_interval.tv_usec = 200000;    setitimer(ITIMER_REAL, &new_value, &old_value);    for(;;);    return 0;}