参考df代码写的一个简单的df命令的源代码

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