linux用c語言擷取系統啟動時長

思路是通過讀取/proc/uptime獲得系統啟動時長。

使用指令cat /proc/uptime

通過man proc可以看到如下的資訊：

/proc/uptime：This file contains two numbers: the uptime of the system (seconds), and the amount of time spent in idle process (seconds).

第一個是系統的啟動時長，第二個是系統的空閑時間。兩個的機關都是秒。

#include <stdio.h>
#include <string.h>
#include <sys/time.h>
#include <stdlib.h>

struct timeval timeget(void)
{
    struct timeval now;
    unsigned char  timestr[] = {};
    unsigned char  uptimestr[] = {};
    unsigned char * dotaddr;
    unsigned long second;
    char error = ;
    FILE * timefile = NULL;

    timefile = fopen("/proc/uptime", "r");
    if(!timefile)
    {
        printf("[%s:line:%d] error opening '/proc/uptime'",__FILE__,__LINE__);
        error = ;
        goto out;
    }

    if( (fread(timestr, sizeof(char), , timefile)) ==  )
    {
        printf("[%s:line:%d] read '/proc/uptime' error",__FILE__,__LINE__);
        error = ;
        goto out;
    }

    dotaddr = strchr(timestr, '.');
    if((dotaddr - timestr + ) < )
        memcpy(uptimestr, timestr, dotaddr - timestr + );
    else
    {
        printf("[%s:line:%d] uptime string is too long",__FILE__,__LINE__);
        error = ;
        goto out;
    }
    uptimestr[dotaddr - timestr + ] = '\0';

out:
    if(error)
    {
        now.tv_sec  = ;
        now.tv_usec = ;
    }
    else
    {
        now.tv_sec  = atol(uptimestr);
        now.tv_usec = ;
    }

    fclose(timefile);
    return now;
}

int main()
{
    struct timeval uptime;

    uptime = timeget();
    printf("uptime = %lu\n", uptime.tv_sec);
    return ;
}
           

運作結果：