linux --> 獲取系統啓動時間

獲取系統啓動時間

1、前言html

  時間對操做系統來講很是重要,從內核級到應用層,時間的表達方式及精度各部相同。linux內核裏面用一個名爲jiffes的常量來計算時間戳。應用層有time、getdaytime等函數。今天須要在應用程序獲取系統的啓動時間,百度了一下,經過sysinfo中的uptime能夠計算出系統的啓動時間。linux

 

2、sysinfo結構函數

  sysinfo結構保持了系統啓動後的信息,主要包括啓動到如今的時間,可用內存空間、共享內存空間、進程的數目等。man sysinfo獲得結果以下所示:post

struct sysinfo {
               long uptime;             /* Seconds since boot */
               unsigned long loads[3];  /* 1, 5, and 15 minute load averages */
               unsigned long totalram;  /* Total usable main memory size */
               unsigned long freeram;   /* Available memory size */
               unsigned long sharedram; /* Amount of shared memory */
               unsigned long bufferram; /* Memory used by buffers */
               unsigned long totalswap; /* Total swap space size */
               unsigned long freeswap;  /* swap space still available */
               unsigned short procs;    /* Number of current processes */
               char _f[22];             /* Pads structure to 64 bytes */
           };

 

3、獲取系統啓動時間測試

  經過sysinfo獲取系統啓動到如今的秒數,用當前時間減去這個秒數即系統的啓動時間。程序以下所示:spa

#include <stdio.h>
#include <sys/sysinfo.h>
#include <time.h>
#include <errno.h>

static int print_system_boot_time()
{
    struct sysinfo info;
    time_t cur_time = 0;
    time_t boot_time = 0;
    struct tm *ptm = NULL;
    if (sysinfo(&info)) {
      fprintf(stderr, "Failed to get sysinfo, errno:%u, reason:%s\n", errno, strerror(errno));
      return -1;
    }
    time(&cur_time);
    if (cur_time > info.uptime) {
      boot_time = cur_time - info.uptime;
    }
    else {
      boot_time = info.uptime - cur_time;
    }
    ptm = gmtime(&boot_time);
    printf("System boot time: %d-%-d-%d %d:%d:%d\n", ptm->tm_year + 1900, ptm->tm_mon + 1, 
        ptm->tm_mday, ptm->tm_hour, ptm->tm_min, ptm->tm_sec); return 0; } int main() { if (print_system_boot_time() != 0) {   return -1; } return 0; }

測試結果以下所:操作系統

 

參考:http://www.cnblogs.com/Anker/p/3527609.htmlcode

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