我打电话来获得系统正常运行时间的API？

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呼叫，或者正常运行时间（1）只是处理从wtmp获得的记录？

Answer 1

系统调用你要找的是SYSINFO（）。

它在sys/sysinfo.h定义

它的签名是： INT SYSINFO（结构SYSINFO *资讯）

由于2.4内核，该结构是这样的：

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

阅读文件/proc/uptime并以秒为单位取第一个十进制数作为正常运行时间。

从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). 

Answer 3

这将是这样的。

有关更多信息，请参阅“man sysinfo”。

Answer 4

还有clock_gettime（可能需要-lrt）。我见过的行为（我不会声称它是有保证的），但给出CLOCK_MONOTONIC，因为clk_id是它返回给定的struct timespec *参数中的系统正常运行时间。

#include <stdio.h> 
#include <time.h> 

int main(int argc, char* argv[]) { 
    struct timespec t; 
    clock_gettime(CLOCK_MONOTONIC, &t); 
    printf("tv_sec=%llu tv_nsec=%llu\n", 
    (unsigned long long)t.tv_sec, 
    (unsigned long long)t.tv_nsec); 
    return 0; 
} 

Answer 5

#include <sys/sysinfo.h> 
#include <sys/types.h> 
#include <stdio.h> 
#include <stdlib.h> 
#include <string.h> 
#include <unistd.h> 
#include <grp.h> 

int main() { 
    struct sysinfo sys_info; 
    struct group* grp; 

    gid_t gid; 
    char** users; 

    int days, hours, mins, x = 1; 

    system("clear"); 
    printf("\033[4;40m   Systems information     \033[0;m \n"); 
    if(sysinfo(&sys_info) != 0) 
    perror("sysinfo"); 

    days = sys_info.uptime/86400; 
    hours = (sys_info.uptime/3600) - (days * 24); 
    mins = (sys_info.uptime/60) - (days * 1440) - (hours * 60); 

    printf("\033[1;33m Uptime: \033[0;36m %ddays, %dhours, %dminutes, %ldseconds \033[0;m \n", 
         days, hours, mins, sys_info.uptime % 60); 

    printf("\033[1;33m Load Avgs: \033[0;m 1min(%ld) 5min(%ld) 15min(%ld) \n", 
      sys_info.loads[0], sys_info.loads[1], sys_info.loads[2]); 

    printf("\033[1;33m Total Ram: \033[0;m %ldk \t Free: %ldk \n", sys_info.totalram/1024, sys_info.freeram/1024); 
    printf(" \033[1;33m Shared Ram: \033[0;m %ldk ", sys_info.sharedram/1024); 
    printf(" Buffered Ram: %ldk \n", sys_info.bufferram/1024); 
    printf("\033[1;33m Total Swap: \033[0;m %ldk \t Free swap: %ldk \n", sys_info.totalswap/1024, sys_info.freeswap/1024); 
    printf("\033[1;33m Total High Memory: \033[0;m %ldk Free high memory: %ldk \033[0;m \n", sys_info.totalhigh/1024, sys_info.freehigh/1024); 
    printf(" \n"); 
    printf("\033[1;44m Total Number of processes: %d \033[0;m \n", sys_info.procs); 
    gid = getgid(); 
    printf(" Group ID: \033[031m %d", gid); 
    if((grp = getgrgid(gid)) == NULL) return 1; 
    printf("\033[0;m Group %s ", grp->gr_name); 
    printf("\n Users in your group "); 
    for(users = grp->gr_mem; *users != NULL; users++,++x); printf("%d", ++x);  
    if(strcmp(grp->gr_passwd,"x") == 0) printf(" Password is protected by shadow file. \n"); 
    else printf("Password: %s ", grp->gr_passwd); 

    return 0; 
}