script to print out file sizes from duplicity difftar and sigtar files

duplicitysizes.py

"""
I use duplicity to back up my files, and cron sends me an email every
day with the output from the backup. Sometimes the size of an
incremental backup is unusually large, and I wonder what made it so big.

This script takes a .difftar.gpg or .sigtar.gpg file and prints the
names of the files in it, listed in decreasing order by size. There's no
error checking of any kind. Enjoy!

Usage:

duplicitysizes.py [.difftar.gpg or .sigtar.gpg files]

This code is public domain, although I would appreciate a mention if you
use this.

--Dan Drake (http://mathsci.kaist.ac.kr/~drake)
"""

import os
import shutil
import subprocess
import sys
import tarfile
import tempfile

def tarfile_to_sorted(fn):
    """
    Returns a list of tuples (filename, kind, size), sorted in
    increasing order by size. "kind" is one of the directories duplicity
    uses in its difftar and sigtar files: "multivol_diff", "deleted",
    "snapshot", etc.
    """
    d = {}
    for f in tarfile.open(fn).getmembers():
        try:
            kind, rest = f.name.split('/', 1)
        except ValueError:
            # sigtar files contain a file named 'snapshot', so there's
            # only value in the split. We just ignore that.
            continue
        if kind.startswith('multivol'):
            name = rest.rsplit('/', 1)[0]
        else:
            name = rest
        size = f.size
        if d.has_key(name):
            oldkind, oldsize = d[name]
            d[name] = (kind, oldsize + size)
        else:
            d[name] = (kind, size)
    return sorted(((k, v[0], v[1]) for k, v in d.iteritems()), key=lambda _: _[2])

if __name__ == '__main__':
    for fn_ in sys.argv[1:]:
        print 'In file {}:'.format(fn_)
        _, fn = tempfile.mkstemp(suffix='.tar.gpg')
        shutil.copy(fn_, fn)
        subprocess.call(['gpg', '--decrypt-files', fn])
        for f, t, s in reversed(tarfile_to_sorted(fn[:-4])):
            print '{:,} {} ({})'.format(s, f, t)
        print
        os.remove(fn[:-4])
        os.remove(fn)