原始碼如下：

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

//檔案系統資訊結構體
struct fileSystem_info{
    char fileSystem_format[8];
    char fileSystem_total_capacity[11];
    char fileSystem_free_capacity[11];
    char fileSystem_permissions[3];
};

/*獲取檔案系統資訊*/
 

int get_fileSystem_info(const char *fileSystem_name, struct fileSystem_info *fi);

/*block to kbyte*/
static unsigned long kscale(unsigned long m_block, unsigned long m_kbyte);

/*convert size to GB MB KB*/
static char *convert_size(float m_size, char *dest);

int main()
{
    char buf[1024];
    struct
 
 fileSystem_info fileSysInfo;
    get_fileSystem_info("/",&fileSysInfo);

    printf("%s\n",fileSysInfo.fileSystem_format);
    printf("%s\n",fileSysInfo.fileSystem_free_capacity);
    printf("%s\n",fileSysInfo.fileSystem_total_capacity);
    printf("%s\n",fileSysInfo.fileSystem_permissions);


    return
 
 0;
}

/*獲取檔案系統資訊*/
int get_fileSystem_info(const char *fileSystem_name,struct fileSystem_info *fi)
{
    struct statfs buf;
    float fileSystem_total_size = 0;
    float fileSystem_free_size = 0;

    if(statfs(fileSystem_name,&buf))
    {
        fprintf(stderr,"statfs %s\n",strerror(errno));
        return -1;
    }

    switch(buf.f_type)
    {
    case 0xEF51:
    case 0xEF53:
        sprintf(fi->fileSystem_format,"EXT");
        break;

    case 0x4d44:
        sprintf(fi->fileSystem_format,"FAT");
        break;

    case 0x5346544e:
        sprintf(fi->fileSystem_format,"NIFS");
        break;

    default:
        sprintf(fi->fileSystem_format,"unknown");
        break;
    }

    bzero(&fi->fileSystem_total_capacity,sizeof(fi->fileSystem_total_capacity));
    bzero(&fi->fileSystem_free_capacity,sizeof(fi->fileSystem_free_capacity));

    printf("blocks %ld\n",buf.f_blocks);
    printf("bfree %ld\n",buf.f_bfree);
    printf("bsize %ld\n",buf.f_bsize);

    fileSystem_total_size =
                    (float)(kscale(buf.f_blocks, buf.f_bsize));
    fileSystem_free_size =
                    (float)(kscale(buf.f_bfree, buf.f_bsize));

    printf("total %f\n",fileSystem_total_size);
    printf("free %f\n",fileSystem_free_size);

    convert_size(fileSystem_total_size,fi->fileSystem_total_capacity);
    convert_size(fileSystem_free_size,fi->fileSystem_free_capacity);

    bzero(fi->fileSystem_permissions,sizeof(fi->fileSystem_permissions));
    sprintf(fi->fileSystem_permissions,"rw");

    return 0;
}

/*block to kbyte*/
static unsigned long kscale(unsigned long m_block, unsigned long m_kbyte)
{

    return ((unsigned long long) m_block * m_kbyte + 1024 / 2 ) /1024;
}

/*convert size to GB MB KB*/
static char *convert_size(float m_size, char *dest)
{
    if((((m_size / 1024.0) / 1024.0)) >= 1.0)
    {
        sprintf(dest,"%0.2fGB",(m_size/1024.0)/1024.0);
    }
    else if((m_size / 1024.0) >= 1.0)
    {
        sprintf(dest,"%0.2fMB",(m_size/1024));
    }
    else
    {
        sprintf(dest,"%0.2fKB",m_size);
    }

    return dest;
}

總結：
1、關於 struct statfs 結構體資訊參考：http://blog.csdn.net/u011641885/article/details/46919027
2、對於fileSystem_total_size 使用float 型別，是為了精確度更高。buysbox 中的 fdisk 原始碼使用的是整型相除，約為4舍五入。
3、kscale 函式中 使用 unsigned long long 型別 是因為 m_block 與 m_byte 原本是long 型，相乘的結果超出了 long 型別的可以表示資料位。