Save disk space by hard-linking multiple Django installations

#!/usr/bin/python

"""
This utility saves disk space if you have multiple Django installations on
your disk.  It will hard link identical files between them.

Note that:

 - you shouldn't edit any hard-linked files, or at least do it with a
   copy-on-write capable editor

 - you need Perl, Python >=2.4 and slocate installed and updatedb run recently
   (usually run regularly from cron)

 - you need the freedups.pl script available from
   http://www.stearns.org/freedups/freedups.pl (this is my chosen duplicate
   file hard linking utility after testing every one out there I could find)

 - freedups.pl will create a md5sum-v1.cache file in your home directory

 - ensure that you have write access to all Django installations

The script was tested on Ubuntu 6.10 Edgy. Modifications may be needed for
other operating systems -- please contribute improvements to the author.

Author: Antti Kaihola <[email protected]>
"""

## Configuration ##############################################################
##
## replace this with the path of freedups.pl on your system
##
FREEDUPS = '/usr/local/bin/freedups.pl'
##
###############################################################################


from subprocess import Popen, PIPE, call
from os.path import basename, exists
from sys import argv, exit, stdout
def out(s): stdout.write(s) ; stdout.flush()

selfpath = argv[0]
selfname = basename(selfpath)

out('%(selfname)s by Antti Kaihola 2007\n\n' % locals())
out('Searching all Django installations on the hard disk...')

try:
    locate = Popen('locate -r /django/core/__init__.py$'.split(), stdout=PIPE)
    django_dirs = [s[:-13] for s in locate.stdout]
except OSError, e:
    exit('\nERROR: locate not found. Please install slocate and run updatedb.'
         '\n       (%s)' % e)

out(' Found %d.\n' % len(django_dirs))
out('Hard linking all identical files between Django installations...\n')

try:
    if call(['perl', FREEDUPS, '-a'] + django_dirs) != 0:
        exit("""
ERROR: freedups.pl couldn't be run. Please download\n
  http://www.stearns.org/freedups/freedups.pl\n
and save it as\n
  %(FREEDUPS)s\n
or indicate a different location by modifying the FREEDUPS variable in\n
  %(selfpath)s""" % locals())
except OSError, e:
    exit('ERROR: perl not found.\n'
         '       (%s)' % e)

out('Done. Have a good day!\n')