关于c: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

#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

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

运行

• testdf执行成果：

$ ./testdfFilesystem                Size      Used Available Use% Mounted onudev                   3.87 GB    0.00 B   3.87 GB   0% /devtmpfs                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/shmtmpfs                  5.00 MB    0.00 B   5.00 MB   0% /run/locktmpfs                  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/12704tmpfs                796.17 MB  980.00 K 795.21 MB   0% /run/snapd/nstmpfs                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执行成果：

$ df -hFilesystem      Size  Used Avail Use% Mounted onudev            3.9G     0  3.9G   0% /devtmpfs           797M  980K  796M   1% /run/dev/vda1        97G   41G   57G  42% /tmpfs           3.9G     0  3.9G   0% /dev/shmtmpfs           5.0M     0  5.0M   0% /run/locktmpfs           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/12704tmpfs           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

欢送关注我的微信公众号【数据库内核】：分享支流开源数据库和存储引擎相干技术。