How do I programmatically get the free disk space for a directory in Linux

Question

Is there a function that returns how much space is free on a drive partition given a directory path?

Answer 1

Use df -h /path/to/directory (mnemonically, "disk free"). The -h flag causes it to use human-readable, base-2 sizes (based on 1024 bytes to the kilobyte) rather than a raw count of 512-byte blocks. You can get base-10 sizes (based on 1000 bytes to the kilobyte - you know, the sizes the hard-disk manufacturers advertise) by using -H.

Example:

$ df -h .
Filesystem     Size   Used  Avail Capacity  Mounted on
/dev/disk0s2  233Gi   82Gi  150Gi    36%    /

To attribute usage, use du -h /path (disk usage).

Answer 2

check man statvfs(2)

I believe you can calculate 'free space' as f_bsize * f_bfree.

NAME
       statvfs, fstatvfs - get file system statistics

SYNOPSIS
       #include <sys/statvfs.h>

       int statvfs(const char *path, struct statvfs *buf);
       int fstatvfs(int fd, struct statvfs *buf);

DESCRIPTION
       The function statvfs() returns information about a mounted file system.
       path is the pathname of any file within the mounted file  system.   buf
       is a pointer to a statvfs structure defined approximately as follows:

           struct statvfs {
               unsigned long  f_bsize;    /* file system block size */
               unsigned long  f_frsize;   /* fragment size */
               fsblkcnt_t     f_blocks;   /* size of fs in f_frsize units */
               fsblkcnt_t     f_bfree;    /* # free blocks */
               fsblkcnt_t     f_bavail;   /* # free blocks for unprivileged users */
               fsfilcnt_t     f_files;    /* # inodes */
               fsfilcnt_t     f_ffree;    /* # free inodes */
               fsfilcnt_t     f_favail;   /* # free inodes for unprivileged users */
               unsigned long  f_fsid;     /* file system ID */
               unsigned long  f_flag;     /* mount flags */
               unsigned long  f_namemax;  /* maximum filename length */
           };