Linux struct Itimerval usage

Look at a piece of code first

#include <stdio.h> #include <time.h> #include <sys/time.h> #include <stdlib.h> #include < signal.h>static int count = 0;void Set_timer () {struct Itimerval itv;itv.it_value.tv_sec = 3;    Timer start after 3 seconds lateritv.it_value.tv_usec = 0;itv.it_interval.tv_sec = 1;itv.it_interval.tv_usec = 0;setiti Mer (Itimer_real,&itv,null);} void Signal_handler (int m) {count + +;p rintf ("%d\n", count);} int main () {signal (Sigalrm,signal_handler); Set_timer (); while (count <); exit (0); return 0;}

This code implements the function: 3 seconds after the timer is started, and then every 1 seconds to the terminal to print the increment value of count, when count to 10 o'clock program exits.

Structure prototype:

struct Itimerval {                struct timeval it_interval;/* Next value */                struct timeval it_value;    /* Current value */            };

struct Timeval {                long tv_sec;                /* seconds */                long tv_usec;               /* microseconds */            };

That

struct Itimerval {    struct timeval it_interval;/* Timer Reset Intermittent value */    struct timeval it_value;    /* Initial value starting first after the timer is installed */};struct timeval {    long tv_sec;                /* sec */    long tv_usec;               /* Subtle (1/1000000) */};

then look at this function:

int Setitimer (int which, const struct Itimerval *value,struct itimerval *ovalue);

Setitimer () sets the struct that value points to the current value of the timer, and returns the original value of the timer if Ovalue is not null.

Which: Intermittent timer type with three options

The Itimer_real//value is 0, the value of the timer decreases in real time, and the signal sent is SIGALRM.
Itimer_virtual//value is 1, Process execution decrements the timer value, the signal sent is SIGVTALRM.
The Itimer_prof//numeric value is 2, and the process and system execution decrements the timer value, and the signal sent is sigprof.

Return Description:
When executed successfully, returns 0. The failed return -1,errno is set to one of the following values
Efault:value or ovalue is not a valid pointer
EINVAL: Its value is not one of itimer_real,itimer_virtual or itimer_prof