程序人生 | UNIX环境高级编程技巧之 df 指令实现

本文首发于 2014-07-10 09:48:48

代码

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#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

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$ gcc -g -Wall testdf.c -o testdf

运行

  • testdf执行效果:
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$ ./testdf
Filesystem Size Used Available Use% Mounted on
udev 3.87 GB 0.00 B 3.87 GB 0% /dev
tmpfs 796.17 MB 980.00 K 795.21 MB 0% /run
/dev/vda1 96.75 GB 40.54 GB 56.19 GB 42% /
tmpfs 3.89 GB 0.00 B 3.89 GB 0% /dev/shm
tmpfs 5.00 MB 0.00 B 5.00 MB 0% /run/lock
tmpfs 3.89 GB 0.00 B 3.89 GB 0% /sys/fs/cgroup
/dev/vda15 104.35 MB 3.86 MB 100.50 MB 4% /boot/efi
/dev/loop1 55.50 MB 55.50 MB 0.00 B 100% /snap/core18/2074
/dev/loop2 70.62 MB 70.62 MB 0.00 B 100% /snap/lxd/16922
/dev/loop4 70.38 MB 70.38 MB 0.00 B 100% /snap/lxd/21029
/dev/loop5 32.38 MB 32.38 MB 0.00 B 100% /snap/snapd/12704
tmpfs 796.17 MB 980.00 K 795.21 MB 0% /run/snapd/ns
tmpfs 796.17 MB 0.00 B 796.17 MB 0% /run/user/1000
/dev/loop6 55.50 MB 55.50 MB 0.00 B 100% /snap/core18/2128
/dev/loop0 32.38 MB 32.38 MB 0.00 B 100% /snap/snapd/12883
  • 原生df执行效果:
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$ df -h
Filesystem Size Used Avail Use% Mounted on
udev 3.9G 0 3.9G 0% /dev
tmpfs 797M 980K 796M 1% /run
/dev/vda1 97G 41G 57G 42% /
tmpfs 3.9G 0 3.9G 0% /dev/shm
tmpfs 5.0M 0 5.0M 0% /run/lock
tmpfs 3.9G 0 3.9G 0% /sys/fs/cgroup
/dev/vda15 105M 3.9M 101M 4% /boot/efi
/dev/loop1 56M 56M 0 100% /snap/core18/2074
/dev/loop2 71M 71M 0 100% /snap/lxd/16922
/dev/loop4 71M 71M 0 100% /snap/lxd/21029
/dev/loop5 33M 33M 0 100% /snap/snapd/12704
tmpfs 797M 0 797M 0% /run/user/1000
/dev/loop6 56M 56M 0 100% /snap/core18/2128
/dev/loop0 33M 33M 0 100% /snap/snapd/12883

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标题 网址
GitHub https://dbkernel.github.io
知乎 https://www.zhihu.com/people/dbkernel/posts
思否(SegmentFault) https://segmentfault.com/u/dbkernel
掘金 https://juejin.im/user/5e9d3ed251882538083fed1f/posts
CSDN https://blog.csdn.net/dbkernel
博客园(cnblogs) https://www.cnblogs.com/dbkernel
文章目录
  1. 1. 代码
  2. 2. 编译
  3. 3. 运行
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