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