Gentoo: Clean up old kernel sources in /usr/src

cleanup-kernel-src.py

#!/usr/bin/env python
from os import chdir, listdir
from os.path import basename, islink, realpath
from shutil import rmtree
import re
import subprocess as sp
import sys


if __name__ == '__main__':
    chdir('/usr/src')
    current = None

    for name in listdir('.'):
        if islink(name):
            current = basename(realpath(name))

    cmd = ['eselect', 'kernel', 'list']
    output = sp.check_output(cmd).decode('utf-8').splitlines()
    for line in output:
        if line.endswith('*'):
            output = line
            break
    eselect_current = re.split(r'\s+', output)[2]

    if not current or not eselect_current or current != eselect_current:
        print('Invalid state. Use `eselect kernel` to set a kernel.',
              file=sys.stderr)
        sys.exit(1)

    print('Current: {}'.format(current), file=sys.stderr)

    removed = False
    for name in listdir('.'):
        if islink(name) or not name.startswith('linux-') or name == current:
            continue
        print('Removing ./{}'.format(name), file=sys.stderr)
        rmtree('./{}'.format(name))
        removed = True

    if not removed:
        print('Found nothing to clean up', file=sys.stderr)