转：参考df代码写的一个简单的df命令的源代码

参考df代码写的一个简单的df命令的源代码

 

整理转载：http://blog.csdn.net/fjb2080/article/details/5990355

作者：飞空静渡

　　df命令可以列出加载的磁盘或各种文件的信息：

　　下面给出一个简单的df的命令的源码，这个源码根据df的源码进行改写，很简单，就一个主文件 :)

#include <stdio.h>  
#include <mntent.h>  
#include <string.h>  
#include <sys/vfs.h>  
static const unsigned long long G = 1024*1024*1024ull;  
static const unsigned long long M = 1024*1024;  
static const unsigned long long K = 1024;  
static char str[20];  

char* kscale(unsigned long b, unsigned long bs)  
{  
    unsigned long long size = b * (unsigned long long)bs;  
    if (size > G)  
    {  
        sprintf(str, "%0.2f GB", size/(G*1.0));  
        return str;  
    }  
    else if (size > M)  
    {  
        sprintf(str, "%0.2f MB", size/(1.0*M));  
        return str;  
    }  
    else if (size > K)  
    {  
        sprintf(str, "%0.2f K", size/(1.0*K));  
        return str;  
    }  
    else  
    {  
        sprintf(str, "%0.2f B", size*1.0);  
        return str;  
    }  
}

int main(int argc, char *argv[])  
{
    FILE* mount_table;  
    struct mntent *mount_entry;  
    struct statfs s;  
    unsigned long blocks_used;  
    unsigned blocks_percent_used;  
    const char *disp_units_hdr = NULL;  
    mount_table = NULL;  
    mount_table = setmntent("/etc/mtab", "r");  
    if (!mount_table)  
    {  
        fprintf(stderr, "set mount entry error\n");  
        return -1;  
    }  
    disp_units_hdr = "     Size";  
    printf("Filesystem           %-15sUsed Available %s Mounted on\n",  
            disp_units_hdr, "Use%");  
    while (1) {  
        const char *device;  
        const char *mount_point;  
        if (mount_table) {  
            mount_entry = getmntent(mount_table);  
            if (!mount_entry) {  
                endmntent(mount_table);  
                break;  
            }  
        }   
        else  
            continue;  
        device = mount_entry->mnt_fsname;  
                                                                                                    mount_point = mount_entry->mnt_dir;  
        //fprintf(stderr, "mount info: device=%s mountpoint=%s\n", device, mount_point);  
        if (statfs(mount_point, &s) != 0)   
        {  
            fprintf(stderr, "statfs failed!\n");      
                continue;  
        }  
        if ((s.f_blocks > 0) || !mount_table )   
        {  
            blocks_used = s.f_blocks - s.f_bfree;  
            blocks_percent_used = 0;  
            if (blocks_used + s.f_bavail)   
            {  
                blocks_percent_used = (blocks_used * 100ULL 
                        + (blocks_used + s.f_bavail)/2
                        ) / (blocks_used + s.f_bavail);  
            }  
            /* GNU coreutils 6.10 skips certain mounts, try to be compatible.  */  
            if (strcmp(device, "rootfs") == 0)  
                continue;  
            if (printf("\n%-20s" + 1, device) > 20)  
                printf("\n%-20s", "");  
            char s1[20];  
            char s2[20];  
            char s3[20];  
            strcpy(s1, kscale(s.f_blocks, s.f_bsize));  
            strcpy(s2, kscale(s.f_blocks - s.f_bfree, s.f_bsize));  
            strcpy(s3, kscale(s.f_bavail, s.f_bsize));  
            printf(" %9s %9s %9s %3u%% %s\n", s1, s2, s3,  
                        blocks_percent_used, mount_point);  
        }  
    }  
    return 0;  
}  

　　编译：g++ -g -Wall main.cpp

　　可以生成一个 a.out 的文件，

　　下面是运行 a.out 和 df -h 的输出对比：

$/tmp/tmp$ df -h
文件系统            容量  已用 可用 已用% 挂载点
/dev/sda7             9.4G  6.5G  2.5G  73% /
none                  1.6G  300K  1.6G   1% /dev
none                  1.6G  212K  1.6G   1% /dev/shm
none                  1.6G  296K  1.6G   1% /var/run
none                  1.6G     0  1.6G   0% /var/lock
none                  1.6G     0  1.6G   0% /lib/init/rw
/dev/sda6             113G   87G   26G  77% /media/work_
/dev/sda9              26G   23G  2.0G  92% /home

 

/tmp/tmp$ ./a.out
Filesystem                Size      Used Available Use% Mounted on
/dev/sda7              9.39 GB   6.45 GB   2.46 GB  72% /
none                   1.59 GB  300.00 K   1.59 GB   0% /dev
none                   1.60 GB 1020.00 K   1.59 GB   0% /dev/shm
none                   1.60 GB  296.00 K   1.59 GB   0% /var/run
none                   1.60 GB    0.00 B   1.60 GB   0% /var/lock
none                   1.60 GB    0.00 B   1.60 GB   0% /lib/init/rw
/dev/sda6            112.62 GB  86.67 GB  25.95 GB  77% /media/work_
/dev/sda9             25.38 GB  22.10 GB   1.99 GB  92% /home

-----------------华---丽---的---分---割---线-----------------

转载时本人将源码中的 /n 改为 \n 。

df 的源码就在 Coreutils 项目中。Coreutils 是 GNU 操作系统的核心工具，包含了许多基本命令，例如cp 、rm 等。想了解更多或者下载最新的源码，请点击这里。