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

Federico A. Ramponi picture Federico A. Ramponi · Nov 23, 2010 · Viewed 125.1k times · Source

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

Mechanical snail picture Mechanical snail · Sep 8, 2012

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)