Find size and free space of the filesystem containing a given file

Question

I'm using Python 2.6 on Linux. What is the fastest way:

• to determine which partition contains a given directory or file?

  For example, suppose that /dev/sda2 is mounted on /home, and /dev/mapper/foo is mounted on /home/foo. From the string "/home/foo/bar/baz" I would like to recover the pair ("/dev/mapper/foo", "home/foo").

• and then, to get usage statistics of the given partition? For example, given /dev/mapper/foo I would like to obtain the size of the partition and the free space available (either in bytes or approximately in megabytes).

Answer 1

This doesn't give the name of the partition, but you can get the filesystem statistics directly using the statvfs Unix system call. To call it from Python, use os.statvfs('/home/foo/bar/baz').

The relevant fields in the result, according to POSIX:

unsigned long f_frsize   Fundamental file system block size.  fsblkcnt_t    f_blocks   Total number of blocks on file system in units of f_frsize.  fsblkcnt_t    f_bfree    Total number of free blocks.  fsblkcnt_t    f_bavail   Number of free blocks available to                           non-privileged process. 

So to make sense of the values, multiply by f_frsize:

import os statvfs = os.statvfs('/home/foo/bar/baz')  statvfs.f_frsize * statvfs.f_blocks     # Size of filesystem in bytes statvfs.f_frsize * statvfs.f_bfree      # Actual number of free bytes statvfs.f_frsize * statvfs.f_bavail     # Number of free bytes that ordinary users                                         # are allowed to use (excl. reserved space)