我打算用什么API来获得系统正常运行时间？

Question

我想从基于Linux的系统上运行的C应用程序中获得系统正常运行时间.我不想调用uptime(1)并解析输出,我想调用我怀疑存在的底层C API.任何人都知道是否有这样的电话,或者正常运行时间(1)只是处理从wtmp获得的记录？

Answer 1

您正在寻找的系统调用是sysinfo().

它在sys/sysinfo.h中定义

它的签名是:int sysinfo(struct sysinfo*info)

从内核2.4开始,结构看起来像这样:

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 */
};

玩得开心!

Answer 2

那将是这样的.

#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 = sysinfo(&s_info);
    if(error != 0)
    {
        printf("code error = %d\n", error);
    }
    return s_info.uptime;
}

有关详细信息,请参阅"man sysinfo".

Answer 3

读取文件/proc/uptime并将第一个十进制数作为正常运行时间,以秒为单位.

来自man 5 proc:

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