linux已开机时间 系统信息

linux 查看系统运行时间 （从开机当现在的开机时间）  

1.uptime命令
输出:16:11:40 up 59 days, 4:21, 2 users, load average: 0.00, 0.01, 0.00

2.查看/proc/uptime文件计算系统启动时间
cat /proc/uptime
输出: 5113396.94 575949.85
第一数字即是系统已运行的时间5113396.94 秒，运用系统工具date即可算出系统启动时间

代码: 
date -d "$(awk -F. '{print $1}' /proc/uptime) second ago" +"%Y-%m-%d %H:%M:%S"

输出: 2008-11-09 11:50:31

3.查看/proc/uptime文件计算系统运行时间

代码:  
cat /proc/uptime| awk -F. '{run_days=$1 / 86400;run_hour=($1 % 86400)/3600;run_minute=($1 % 3600)/60;run_second=$1 % 60;printf("系统已运行：%d天%d时%d分%d秒",run_days,run_hour,run_minute,run_second)}'

输出:系统已运行：59天4时13分9秒

这样你就能轻松地应用Linux查看系统时间。

c代码：

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 */
    unsigned long totalhigh; /* Total high memory size */
    unsigned long freehigh;  /* Available high memory size */
    unsigned int mem_unit;   /* Memory unit size in bytes */
    char _f[20-2*sizeof(long)-sizeof(int)]; /* Padding for libc5 */
};

　　

#include <stdio.h>
#include <time.h>
#include <stdio.h>
#include <errno.h>
#include <linux/unistd.h>       /* for _syscallX macros/related stuff */
#include <linux/kernel.h>       /* for struct sysinfo */
#include <sys/sysinfo.h>

long get_uptime()
{
    struct sysinfo s_info;
    int error;
    error = sysinfo(&s_info);
    if(error != 0)
    {
        printf("code error = %d
", error);
    }
    return s_info.uptime;
}

long out_sys(){
	  /* Conversion constants. */
	  const long minute = 60;
	  const long hour = minute * 60;
	  const long day = hour * 24;
	  const double megabyte = 1024 * 1024;
	  /* Obtain system statistics. */
	  struct sysinfo si;
	  sysinfo (&si);
	  /* Summarize interesting values. */
	  printf ("system uptime : %ld days, %ld:%02ld:%02ld
",
	          si.uptime / day, (si.uptime % day) / hour,
	          (si.uptime % hour) / minute, si.uptime % minute);
	  printf ("total RAM     : %5.1f MB
", si.totalram / megabyte);
	  printf ("free RAM      : %5.1f MB
", si.freeram / megabyte);
	  printf ("process count : %d
", si.procs);
}

int main(int argc, char* argv[]) {
  struct timespec t;
  clock_gettime(CLOCK_MONOTONIC, &t);
  printf("tv_sec=%llu tv_nsec=%llu
 uptime time:%llu
",
    (unsigned long long)t.tv_sec,
    (unsigned long long)t.tv_nsec,
    get_uptime());

  out_sys();
  return 0;
}