linux中使用定時器

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1.使用14號訊號SIGALRM，調用alarm函數

#include <stdio.h>#include <stdlib.h>#include <string.h>#include <unistd.h>#include <signal.h>void handle(int signum){ printf("hello\n");}int main(int argc, const char *argv[]){    signal(SIGALRM, handle);    while(1)    {        alarm(3);        sleep(3);    }    return 0;}

//每隔3秒向自身發送一個SIGALRM訊號，signal收到 SIGALRM訊號後調用handle進行處理

--》alarm只能精確到秒

2.setitimer  -->也是通過向自身發送訊號進行處理的，不過可以精確到毫妙層級

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

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_VIR-
                      TUAL, this timer is usually used to profile the  time  spent  by
                      the  application in user and kernel space.  SIGPROF is delivered
                      upon expiration.

 struct itimerval {
               struct timeval it_interval; /* next value */
               struct timeval it_value;    /* current value */
           };

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

--》3種模式產生3中不同的訊號，使用方法類似

在該例子中，每隔一秒發出一個SIGALRM，每隔0.5秒發出一個SIGVTALRM訊號：#include <stdio.h>#include <stdlib.h>#include <unistd.h>#include <signal.h>#include <time.h>#include <sys/time.h>int sec;void sigroutine(int signo){switch (signo){case SIGALRM:printf("Catch a signal -- SIGALRM \n");signal(SIGALRM, sigroutine);break;case SIGVTALRM:printf("Catch a signal -- SIGVTALRM \n");signal(SIGVTALRM, sigroutine);break;}fflush(stdout);return;}int main(){struct itimerval value, ovalue, value2; //(1)sec = 5;printf("process id is %d\n", getpid());signal(SIGALRM, sigroutine);signal(SIGVTALRM, sigroutine);value.it_value.tv_sec = 1;value.it_value.tv_usec = 0;value.it_interval.tv_sec = 1;value.it_interval.tv_usec = 0;setitimer(ITIMER_REAL, &value, &ovalue); //(2)value2.it_value.tv_sec = 0;value2.it_value.tv_usec = 500000;value2.it_interval.tv_sec = 0;value2.it_interval.tv_usec = 500000;setitimer(ITIMER_VIRTUAL, &value2, &ovalue);for(;;);}

3.timerfd_create   timerfd_settime   -->通過時間設定fd可讀，然後通過select輪詢，調用處理函數

#include <stdio.h>#include <stdlib.h>#include <string.h>#include <sys/timerfd.h>#include <sys/time.h>#include <sys/types.h>#include <unistd.h>#include <errno.h>#define ERR_EXIT(m)     do {         perror(m);        exit(EXIT_FAILURE);    }while(0)int main(int argc, const char *argv[]){    struct itimerspec time;    time.it_value.tv_sec = 5;    time.it_interval.tv_sec = 2;    int timerfd = timerfd_create(CLOCK_REALTIME, 0);    if(timerfd == -1)        ERR_EXIT("timerfd_create");    if(timerfd_settime(timerfd, 0, &time, NULL) == -1)        ERR_EXIT("timerfd_settime");    fd_set read1, ready;    FD_ZERO(&read1);    FD_SET(timerfd, &read1);    char buf[1024];    struct timeval time_select;    while(1)    {        time_select.tv_sec = 3;//必須定義在while內部        time_select.tv_usec = 11;        ready = read1;        int nready = select(timerfd + 1, &ready, NULL, NULL, &time_select);//設定為一直阻塞        if(nready == -1)            ERR_EXIT("select");        else if(nready == 0)            printf("timeout");        else        {            if(-1 == read(timerfd, buf, sizeof buf))            {                printf("%s\n", strerror(errno));//列印錯誤資訊                ERR_EXIT("read");            }            printf("come\n");        }    }    return 0;}

4.直接使用select   -->精確到毫秒層級

int msSleep(long ms) {    struct timeval tv;    tv.tv_sec = 0;    tv.tv_usec = ms;     return select(0, NULL, NULL, NULL, &tv);}

其他資料：

http://www.cppblog.com/CppExplore/archive/2008/04/02/46111.html 



linux中使用定時器