tools.py

#    Back In Time
#    Copyright (C) 2008-2022 Oprea Dan, Bart de Koning, Richard Bailey, Germar Reitze, Taylor Raack
#
#    This program is free software; you can redistribute it and/or modify
#    it under the terms of the GNU General Public License as published by
#    the Free Software Foundation; either version 2 of the License, or
#    (at your option) any later version.
#
#    This program is distributed in the hope that it will be useful,
#    but WITHOUT ANY WARRANTY; without even the implied warranty of
#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#    GNU General Public License for more details.
#
#    You should have received a copy of the GNU General Public License along
#    with this program; if not, write to the Free Software Foundation, Inc.,
#    51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.


import os
import sys
import pathlib
import subprocess
import shlex
import signal
import re
import errno
import gzip
import tempfile
try:
    from collections.abc import MutableSet
except ImportError:
    from collections import MutableSet
import hashlib
import ipaddress
import atexit
from datetime import datetime
from packaging.version import Version
from time import sleep
keyring = None
keyring_warn = False
try:
    if os.getenv('BIT_USE_KEYRING', 'true') == 'true' and os.geteuid() != 0:
        import keyring
except:
    keyring = None
    os.putenv('BIT_USE_KEYRING', 'false')
    keyring_warn = True

# getting dbus imports to work in Travis CI is a huge pain
# use conditional dbus import
ON_TRAVIS = os.environ.get('TRAVIS', 'None').lower() == 'true'
ON_RTD = os.environ.get('READTHEDOCS', 'None').lower() == 'true'

try:
    import dbus
except ImportError:
    if ON_TRAVIS or ON_RTD:
        #python-dbus doesn't work on Travis yet.
        dbus = None
    else:
        raise

import configfile
import logger
import bcolors
from applicationinstance import ApplicationInstance
from exceptions import Timeout, InvalidChar, InvalidCmd, LimitExceeded, PermissionDeniedByPolicy

DISK_BY_UUID = '/dev/disk/by-uuid'

def sharePath():
    """
    Get BackInTimes installation base path.

    If running from source return default '/usr/share'

    Returns:
        str:    share path like::

                    /usr/share
                    /usr/local/share
                    /opt/usr/share
    """
    share = os.path.abspath(os.path.join(__file__, os.pardir, os.pardir, os.pardir))
    if os.path.basename(share) == 'share':
        return share
    else:
        return '/usr/share'

def backintimePath(*path):
    """
    Get path inside 'backintime' install folder.

    Args:
        *path (str):    paths that should be joind to 'backintime'

    Returns:
        str:            'backintime' child path like::

                            /usr/share/backintime/common
                            /usr/share/backintime/qt
    """
    return os.path.abspath(os.path.join(__file__, os.pardir, os.pardir, *path))

def registerBackintimePath(*path):
    """
    Add BackInTime path ``path`` to :py:data:`sys.path` so subsequent imports
    can discover them.

    Args:
        *path (str):    paths that should be joind to 'backintime'

    Note:
        Duplicate in :py:func:`qt/qttools.py` because modules in qt folder
        would need this to actually import :py:mod:`tools`.
    """
    path = backintimePath(*path)
    if not path in sys.path:
        sys.path.insert(0, path)

def runningFromSource():
    """
    Check if BackInTime is running from source (without installing).

    Returns:
        bool:   ``True`` if BackInTime is running from source
    """
    return os.path.isfile(backintimePath('common', 'backintime'))

def addSourceToPathEnviron():
    """
    Add 'backintime/common' path to 'PATH' environ variable.
    """
    source = backintimePath('common')
    path = os.getenv('PATH')
    if path and source not in path.split(':'):
        os.environ['PATH'] = '%s:%s' %(source, path)

def gitRevisionAndHash():
    """
    Get the current Git Branch and the last HashID (shot form) if running
    from source.

    Returns:
        tuple:  two items of either :py:class:`str` instance if running from
                source or ``None``
    """
    ref, hashid = None, None
    gitPath = os.path.abspath(os.path.join(__file__, os.pardir, os.pardir, '.git'))
    headPath = os.path.join(gitPath, 'HEAD')
    refPath = ''
    if not os.path.isdir(gitPath):
        return (ref, hashid)
    try:
        with open(headPath, 'rt') as f:
            refPath = f.read().strip('\n')
            if refPath.startswith('ref: '):
                refPath = refPath[5:]
            if refPath:
                refPath = os.path.join(gitPath, refPath)
                ref = os.path.basename(refPath)
    except Exception as e:
        pass
    if os.path.isfile(refPath):
        try:
            with open(refPath, 'rt') as f:
                hashid = f.read().strip('\n')[:7]
        except:
            pass
    return (ref, hashid)


def readFile(path, default=None):
    """
    Read the file in ``path`` or its '.gz' compressed variant and return its
    content or ``default`` if ``path`` does not exist.

    Args:
        path (str):             full path to file that should be read.
                                '.gz' will be added automatically if the file
                                is compressed
        default (str):          default if ``path`` does not exist

    Returns:
        str:                    content of file in ``path``
    """
    ret_val = default

    try:
        if os.path.exists(path):

            with open(path) as f:
                ret_val = f.read()

        elif os.path.exists(path + '.gz'):

            with gzip.open(path + '.gz', 'rt') as f:
                ret_val = f.read()

    except:
        pass

    return ret_val


def readFileLines(path, default = None):
    """
    Read the file in ``path`` or its '.gz' compressed variant and return its
    content as a list of lines or ``default`` if ``path`` does not exist.

    Args:
        path (str):             full path to file that should be read.
                                '.gz' will be added automatically if the file
                                is compressed
        default (list):         default if ``path`` does not exist

    Returns:
        list:                   content of file in ``path`` splitted by lines.
    """
    ret_val = default

    try:
        if os.path.exists(path):
            with open(path) as f:
                ret_val = [x.rstrip('\n') for x in f.readlines()]
        elif os.path.exists(path + '.gz'):
            with gzip.open(path + '.gz', 'rt') as f:
                ret_val = [x.rstrip('\n') for x in f.readlines()]
    except:
        pass

    return ret_val

def checkCommand(cmd):
    """
    Check if command ``cmd`` is a file in 'PATH' environ.

    Args:
        cmd (str):  command

    Returns:
        bool:       ``True`` if command ``cmd`` is in 'PATH' environ
    """
    cmd = cmd.strip()

    if not cmd:
        return False

    if os.path.isfile(cmd):
        return True
    return not which(cmd) is None

def which(cmd):
    """
    Get the fullpath of executable command ``cmd``. Works like
    command-line 'which' command.

    Args:
        cmd (str):  command

    Returns:
        str:        fullpath of command ``cmd`` or ``None`` if command is
                    not available
    """
    pathenv = os.getenv('PATH', '')
    path = pathenv.split(":")
    common = backintimePath('common')
    if runningFromSource() and common not in path:
        path.insert(0, common)
    for directory in path:
        fullpath = os.path.join(directory, cmd)
        if os.path.isfile(fullpath) and os.access(fullpath, os.X_OK):
            return fullpath
    return None

def makeDirs(path):
    """
    Create directories ``path`` recursive and return success.

    Args:
        path (str): fullpath to directories that should be created

    Returns:
        bool:       ``True`` if successful
    """
    path = path.rstrip(os.sep)
    if not path:
        return False

    if os.path.isdir(path):
        return True
    else:
        try:
            os.makedirs(path)
        except Exception as e:
            logger.error("Failed to make dirs '%s': %s"
                         %(path, str(e)), traceDepth = 1)
    return os.path.isdir(path)

def mkdir(path, mode = 0o755, enforce_permissions = True):
    """
    Create directory ``path``.

    Args:
        path (str): full path to directory that should be created
        mode (int): numeric permission mode

    Returns:
        bool:       ``True`` if successful
    """
    if os.path.isdir(path):
        try:
            if enforce_permissions:
                os.chmod(path, mode)
        except:
            return False
        return True
    else:
        os.mkdir(path, mode)
        if mode & 0o002 == 0o002:
            #make file world (other) writable was requested
            #debian and ubuntu won't set o+w with os.mkdir
            #this will fix it
            os.chmod(path, mode)
    return os.path.isdir(path)


def pids():
    """
    List all PIDs currently running on the system.

    Returns:
        list:   PIDs as int
    """
    return [int(x) for x in os.listdir('/proc') if x.isdigit()]


def processStat(pid):
    """
    Get the stat's of the process with ``pid``.

    Args:
        pid (int):  Process Indicator

    Returns:
        str:        stat from /proc/PID/stat
    """
    try:
        with open('/proc/{}/stat'.format(pid), 'rt') as f:
            return f.read()

    except OSError as e:
        logger.warning('Failed to read process stat from {}: [{}] {}'
                       .format(e.filename, e.errno, e.strerror))
        return ''


def processPaused(pid):
    """
    Check if process ``pid`` is paused (got signal SIGSTOP).

    Args:
        pid (int):  Process Indicator

    Returns:
        bool:       True if process is paused
    """
    m = re.match(r'\d+ \(.+\) T', processStat(pid))

    return bool(m)


def processName(pid):
    """
    Get the name of the process with ``pid``.

    Args:
        pid (int):  Process Indicator

    Returns:
        str:        name of the process
    """
    m = re.match(r'.*\((.+)\).*', processStat(pid))

    if m:
        return m.group(1)


def processCmdline(pid):
    """
    Get the cmdline (command that spawnd this process) of the process with
    ``pid``.

    Args:
        pid (int):  Process Indicator

    Returns:
        str:        cmdline of the process
    """
    try:
        with open('/proc/{}/cmdline'.format(pid), 'rt') as f:
            return f.read().strip('\n')
    except OSError as e:
        logger.warning('Failed to read process cmdline from {}: [{}] {}'.format(e.filename, e.errno, e.strerror))
        return ''

def pidsWithName(name):
    """
    Get all processes currently running with name ``name``.

    Args:
        name (str): name of a process like 'python3' or 'backintime'

    Returns:
        list:       PIDs as int
    """
    # /proc/###/stat stores just the first 16 chars of the process name
    return [x for x in pids() if processName(x) == name[:15]]

def processExists(name):
    """
    Check if process ``name`` is currently running.

    Args:
        name (str): name of a process like 'python3' or 'backintime'

    Returns:
        bool:       ``True`` if there is a process running with ``name``
    """
    return len(pidsWithName(name)) > 0

def processAlive(pid):
    """
    Check if the process with PID ``pid`` is alive.

    Args:
        pid (int):  Process Indicator

    Returns:
        bool:       ``True`` if the process with PID ``pid`` is alive

    Raises:
        ValueError: If ``pid`` is 0 because 'kill(0, SIG)' would send SIG to all
                    processes
    """
    if pid < 0:
        return False
    elif pid == 0:
        raise ValueError('invalid PID 0')
    else:
        try:
            os.kill(pid, 0) #this will raise an exception if the pid is not valid
        except OSError as err:
            if err.errno == errno.ESRCH:
                # ESRCH == No such process
                return False
            elif err.errno == errno.EPERM:
                # EPERM clearly means there's a process to deny access to
                return True
            else:
                raise
        else:
            return True

def checkXServer():
    """
    Check if there is a X11 server running on this system.

    Returns:
        bool:   ``True`` if X11 server is running
    """
    if checkCommand('xdpyinfo'):
        proc = subprocess.Popen(['xdpyinfo'],
                                stdout = subprocess.DEVNULL,
                                stderr = subprocess.DEVNULL)
        proc.communicate()
        return proc.returncode == 0
    else:
        return False

def preparePath(path):
    """
    Removes trailing slash '/' from ``path``.

    Args:
        path (str): absolut path

    Returns:
        str:        path ``path`` without trailing but with leading slash
    """
    path = path.strip("/")
    path = os.sep + path
    return path

def powerStatusAvailable():
    """
    Check if org.freedesktop.UPower is available so that
    :py:func:`tools.onBattery` would return the correct power status.

    Returns:
        bool:   ``True`` if :py:func:`tools.onBattery` can report power status
    """
    if dbus:
        try:
            bus = dbus.SystemBus()
            proxy = bus.get_object('org.freedesktop.UPower',
                                   '/org/freedesktop/UPower')
            return 'OnBattery' in proxy.GetAll('org.freedesktop.UPower',
                            dbus_interface = 'org.freedesktop.DBus.Properties')
        except dbus.exceptions.DBusException:
            pass
    return False

def onBattery():
    """
    Checks if the system is on battery power.

    Returns:
        bool:   ``True`` if system is running on battery
    """
    if dbus:
        try:
            bus = dbus.SystemBus()
            proxy = bus.get_object('org.freedesktop.UPower',
                                   '/org/freedesktop/UPower')
            return bool(proxy.Get('org.freedesktop.UPower',
                                  'OnBattery',
                                  dbus_interface = 'org.freedesktop.DBus.Properties'))
        except dbus.exceptions.DBusException:
            pass
    return False

def rsyncCaps(data = None):
    """
    Get capabilities of the installed rsync binary. This can be different from
    version to version and also on build arguments used when building rsync.

    Args:
        data (str): 'rsync --version' output. This is just for unittests.

    Returns:
        list:       List of str with rsyncs capabilities
    """
    if not data:
        proc = subprocess.Popen(['rsync', '--version'],
                                stdout = subprocess.PIPE,
                                universal_newlines = True)
        data = proc.communicate()[0]
    caps = []
    #rsync >= 3.1 does provide --info=progress2
    matchers = [r'rsync\s*version\s*(\d\.\d)', r'rsync\s*version\s*v(\d\.\d.\d)']
    for matcher in matchers:
        m = re.match(matcher, data)
        if m and Version(m.group(1)) >= Version('3.1'):
            caps.append('progress2')
            break

    #all other capabilities are separated by ',' between
    #'Capabilities:' and '\n\n'
    m = re.match(r'.*Capabilities:(.+)\n\n.*', data, re.DOTALL)
    if not m:
        return caps

    for line in m.group(1).split('\n'):
        caps.extend([i.strip(' \n') for i in line.split(',') if i.strip(' \n')])
    return caps


def rsyncPrefix(config,
                no_perms=True,
                use_mode=['ssh', 'ssh_encfs'],
                progress=True):
    """
    Get rsync command and all args for creating a new snapshot. Args are
    based on current profile in ``config``.

    Args:
        config (config.Config): current config
        no_perms (bool):        don't sync permissions (--no-p --no-g --no-o)
                                if ``True``.
                                :py:func:`config.Config.preserveAcl` == ``True`` or
                                :py:func:`config.Config.preserveXattr` == ``True``
                                will overwrite this to ``False``
        use_mode (list):        if current mode is in this list add additional
                                args for that mode
        progress (bool):        add '--info=progress2' to show progress

    Returns:
        list:                   rsync command with all args but without
                                --include, --exclude, source and destination
    """
    caps = rsyncCaps()
    cmd = []

    if config.nocacheOnLocal():
        cmd.append('nocache')

    cmd.append('rsync')

    cmd.extend(('--recursive',     # recurse into directories
                '--times',          # preserve modification times
                '--devices',        # preserve device files (super-user only)
                '--specials',       # preserve special files
                '--hard-links',     # preserve hard links
                '--human-readable'))# numbers in a human-readable format

    if config.useChecksum() or config.forceUseChecksum:
        cmd.append('--checksum')

    if config.copyUnsafeLinks():
        cmd.append('--copy-unsafe-links')

    if config.copyLinks():
        cmd.append('--copy-links')
    else:
        cmd.append('--links')

    if config.preserveAcl() and "ACLs" in caps:
        cmd.append('--acls')  # preserve ACLs (implies --perms)
        no_perms = False

    if config.preserveXattr() and "xattrs" in caps:
        cmd.append('--xattrs')  # preserve extended attributes
        no_perms = False

    if no_perms:
        cmd.extend(('--no-perms', '--no-group', '--no-owner'))
    else:
        cmd.extend(('--perms',          # preserve permissions
                    '--executability',  # preserve executability
                    '--group',         # preserve group
                    '--owner'))         # preserve owner (super-user only)

    if progress and 'progress2' in caps:
        cmd.extend(('--info=progress2',
                    '--no-inc-recursive'))

    if config.bwlimitEnabled():
        cmd.append('--bwlimit=%d' % config.bwlimit())

    if config.rsyncOptionsEnabled():
        cmd.extend(shlex.split(config.rsyncOptions()))

    cmd.extend(rsyncSshArgs(config, use_mode))
    return cmd


def rsyncSshArgs(config, use_mode=['ssh', 'ssh_encfs']):
    """
    Get SSH args for rsync based on current profile in ``config``.

    Args:
        config (config.Config): Current config instance.
        use_mode (list):        If the profiles current mode is in this list
                                add additional args.

    Returns:
        list:                   List of rsync args related to SSH.
    """

    cmd = []

    mode = config.snapshotsMode()

    if mode in ['ssh', 'ssh_encfs'] and mode in use_mode:
        ssh = config.sshCommand(user_host=False,
                                ionice=False,
                                nice=False)

        cmd.append('--rsh=' + ' '.join(ssh))

        if config.niceOnRemote() \
           or config.ioniceOnRemote() \
           or config.nocacheOnRemote():

            rsync_path = '--rsync-path='

            if config.niceOnRemote():
                rsync_path += 'nice -n 19 '

            if config.ioniceOnRemote():
                rsync_path += 'ionice -c2 -n7 '

            if config.nocacheOnRemote():
                rsync_path += 'nocache '

            rsync_path += 'rsync'

            cmd.append(rsync_path)

    return cmd


def rsyncRemove(config, run_local = True):
    """
    Get rsync command and all args for removing snapshots with rsync.

    Args:
        config (config.Config): current config
        run_local (bool):       if True and current mode is ``ssh``
                                or ``ssh_encfs`` this will add SSH options

    Returns:
        list:                   rsync command with all args
    """
    cmd = ['rsync', '-a', '--delete']
    if run_local:
        cmd.extend(rsyncSshArgs(config))
    return cmd

#TODO: check if we really need this
def tempFailureRetry(func, *args, **kwargs):
    while True:
        try:
            return func(*args, **kwargs)
        except (os.error, IOError) as ex:
            if ex.errno == errno.EINTR:
                continue
            else:
                raise

def md5sum(path):
    """
    Calculate md5sum for file in ``path``.

    Args:
        path (str): full path to file

    Returns:
        str:        md5sum of file
    """
    md5 = hashlib.md5()
    with open(path, 'rb') as f:
        while True:
            data = f.read(4096)
            if not data:
                break
            md5.update(data)
    return md5.hexdigest()

def checkCronPattern(s):
    """
    Check if ``s`` is a valid cron pattern.
    Examples::

        0,10,13,15,17,20,23
        */6

    Args:
        s (str):    pattern to check

    Returns:
        bool:       ``True`` if ``s`` is a valid cron pattern
    """
    if s.find(' ') >= 0:
        return False
    try:
        if s.startswith('*/'):
            if s[2:].isdigit() and int(s[2:]) <= 24:
                return True
            else:
                return False
        for i in s.split(','):
            if i.isdigit() and int(i) <= 24:
                continue
            else:
                return False
        return True
    except ValueError:
        return False

#TODO: check if this is still necessary
def checkHomeEncrypt():
    """
    Return ``True`` if users home is encrypted
    """
    home = os.path.expanduser('~')
    if not os.path.ismount(home):
        return False
    if checkCommand('ecryptfs-verify'):
        try:
            subprocess.check_call(['ecryptfs-verify', '--home'],
                                    stdout=subprocess.DEVNULL,
                                    stderr=subprocess.DEVNULL)
        except subprocess.CalledProcessError:
            pass
        else:
            return True
    if checkCommand('encfs'):
        proc = subprocess.Popen(['mount'], stdout=subprocess.PIPE, universal_newlines = True)
        mount = proc.communicate()[0]
        r = re.compile('^encfs on %s type fuse' % home)
        for line in mount.split('\n'):
            if r.match(line):
                return True
    return False

def envLoad(f):
    """
    Load environ variables from file ``f`` into current environ.
    Do not overwrite existing environ variables.

    Args:
        f (str):    full path to file with environ variables
    """
    env = os.environ.copy()
    env_file = configfile.ConfigFile()
    env_file.load(f, maxsplit = 1)
    for key in env_file.keys():
        value = env_file.strValue(key)
        if not value:
            continue
        if not key in list(env.keys()):
            os.environ[key] = value
    del(env_file)

def envSave(f):
    """
    Save environ variables to file that are needed by cron
    to connect to keyring. This will only work if the user is logged in.

    Args:
        f (str):    full path to file for environ variables
    """
    env = os.environ.copy()
    env_file = configfile.ConfigFile()
    for key in ('GNOME_KEYRING_CONTROL', 'DBUS_SESSION_BUS_ADDRESS', \
                'DBUS_SESSION_BUS_PID', 'DBUS_SESSION_BUS_WINDOWID', \
                'DISPLAY', 'XAUTHORITY', 'GNOME_DESKTOP_SESSION_ID', \
                'KDE_FULL_SESSION'):
        if key in env:
            env_file.setStrValue(key, env[key])

    env_file.save(f)

def keyringSupported():
    if keyring is None:
        logger.debug('No keyring due to import error.')
        return False
    backends = []
    try: backends.append(keyring.backends.SecretService.Keyring)
    except: pass
    try: backends.append(keyring.backends.Gnome.Keyring)
    except: pass
    try: backends.append(keyring.backends.kwallet.Keyring)
    except: pass
    try: backends.append(keyring.backends.kwallet.DBusKeyring)
    except: pass
    try: backends.append(keyring.backend.SecretServiceKeyring)
    except: pass
    try: backends.append(keyring.backend.GnomeKeyring)
    except: pass
    try: backends.append(keyring.backend.KDEKWallet)
    except: pass
    try:
        displayName = keyring.get_keyring().__module__
    except:
        displayName = str(keyring.get_keyring())
    if backends and isinstance(keyring.get_keyring(), tuple(backends)):
        logger.debug("Found appropriate keyring '{}'".format(displayName))
        return True
    logger.debug("No appropriate keyring found. '{}' can't be used with BackInTime".format(displayName))
    return False

def password(*args):
    if not keyring is None:
        return keyring.get_password(*args)
    return None

def setPassword(*args):
    if not keyring is None:
        return keyring.set_password(*args)
    return False

def mountpoint(path):
    """
    Get the mountpoint of ``path``. If your HOME is on a separate partition
    mountpoint('/home/user/foo') would return '/home'.

    Args:
        path (str): full path

    Returns:
        str:        mountpoint of the filesystem
    """
    path = os.path.realpath(os.path.abspath(path))
    while path != os.path.sep:
        if os.path.ismount(path):
            return path
        path = os.path.abspath(os.path.join(path, os.pardir))
    return path

def decodeOctalEscape(s):
    """
    Decode octal-escaped characters with its ASCII dependance.
    For example '\040' will be a space ' '

    Args:
        s (str):    string with or without octal-escaped characters

    Returns:
        str:        human readable string
    """
    def repl(m):
        return chr(int(m.group(1), 8))
    return re.sub(r'\\(\d{3})', repl, s)

def mountArgs(path):
    """
    Get all /etc/mtab args for the filesystem of ``path`` as a list.
    Example::

        [DEVICE,      MOUNTPOINT, FILESYSTEM_TYPE, OPTIONS,    DUMP, PASS]
        ['/dev/sda3', '/',        'ext4',          'defaults', '0',  '0']
        ['/dev/sda1', '/boot',    'ext4',          'defaults', '0',  '0']

    Args:
        path (str): full path

    Returns:
        list:       mount args
    """
    mp = mountpoint(path)
    
    with open('/etc/mtab', 'r') as mounts:

        for line in mounts:
            args = line.strip('\n').split(' ')

            if len(args) >= 2:
                args[1] = decodeOctalEscape(args[1])

                if args[1] == mp:
                    return args

    return None

def device(path):
    """
    Get the device for the filesystem of ``path``.
    Example::

        /dev/sda1
        /dev/mapper/vglinux
        proc

    Args:
        path (str): full path

    Returns:
        str:        device
    """
    args = mountArgs(path)

    if args:
        return args[0]

    return None

def filesystem(path):
    """
    Get the filesystem type for the filesystem of ``path``.

    Args:
        path (str): full path

    Returns:
        str:        filesystem
    """
    args = mountArgs(path)
    if args and len(args) >= 3:
        return args[2]
    return None

def _uuidFromDev_via_filesystem(dev):
    """Get the UUID for the block device ``dev`` from ``/dev/disk/by-uuid`` in
    the filesystem.

    Args:
        dev (pathlib.Path): The block device path (e.g. ``/dev/sda1``).

    Returns:
        str: The UUID or ``None`` if nothing found.
    """


    # /dev/disk/by-uuid
    path_DISK_BY_UUID = pathlib.Path(DISK_BY_UUID)

    if not path_DISK_BY_UUID.exists():
        return None

    # Each known uuid
    for uuid_symlink in path_DISK_BY_UUID.glob('*'):

        # Resolve the symlink (get it's target) to get the real device name
        # and compare it with the device we are looking for
        if dev == uuid_symlink.resolve():

            # e.g. 'c7aca0a7-89ed-43f0-a4f9-c744dfe673e0'
            return uuid_symlink.name

    # Nothing found
    return None

def _uuidFromDev_via_blkid_command(dev):
    """Get the UUID for the block device ``dev`` via the extern command
    ``blkid``.

    Hint:
        On most systems the ``blkid`` command is available only for the
        super-user (e.g. via ``sudo``).

    Args:
        dev (pathlib.Path): The block device path (e.g. ``/dev/sda1``).

    Returns:
        str: The UUID or ``None`` if nothing found.
    """

    # Call "blkid" command
    try:
        # If device does not exist, blkid will exit with a non-zero code
        output = subprocess.check_output(['blkid', dev],
                                        stderr = subprocess.DEVNULL,
                                        universal_newlines=True)

    except (subprocess.CalledProcessError, FileNotFoundError):
        return None

    # Parse the commands output for a UUID
    try:
        return re.findall(r'.*\sUUID=\"([^\"]*)\".*', output)[0]
    except IndexError:
        # nothing found via the regex pattern
        pass

    return None

def _uuidFromDev_via_udevadm_command(dev):
    """Get the UUID for the block device ``dev`` via the extern command
    ``udevadm``.

    Args:
        dev (pathlib.Path): The block device path (e.g. ``/dev/sda1``).

    Returns:
        str: The UUID or ``None`` if nothing found.
    """
    # Call "udevadm" command
    try:
        output = subprocess.check_output(['udevadm', 'info', f'--name={dev}'],
                                        stderr = subprocess.DEVNULL,
                                        universal_newlines=True)

    except (subprocess.CalledProcessError, FileNotFoundError):
        return None

    # Parse the commands output for a UUID
    try:
        return re.findall(r'.*?ID_FS_UUID=(\S+)', output)[0]
    except IndexError:
        # nothing found via the regex pattern
        pass

    return None


def uuidFromDev(dev):
    """
    Get the UUID for the block device ``dev``.

    Args:
        dev (str, pathlib.Path):  block device path

    Returns:
        str:        UUID
    """

    # handle Path objects only
    if not isinstance(dev, pathlib.Path):
        dev = pathlib.Path(dev)

    if dev.exists():
        dev = dev.resolve()  # when /dev/sda1 is a symlink

        # Look at /dev/disk/by-uuid/
        uuid = _uuidFromDev_via_filesystem(dev)
        if uuid:
            return uuid

        # Try extern command "blkid"
        uuid = _uuidFromDev_via_blkid_command(dev)
        if uuid:
            return uuid

    # "dev" doesn't exist in the filesystem

    # Try "udevadm" command at the end
    return _uuidFromDev_via_udevadm_command(dev)

def uuidFromPath(path):
    """
    Get the UUID for the for the filesystem of ``path``.

    Args:
        path (str): full path

    Returns:
        str:        UUID
    """
    return uuidFromDev(device(path))

def filesystemMountInfo():
    """
    Get a dict of mount point string -> dict of filesystem info for
    entire system.

    Returns:
        dict:   {MOUNTPOINT: {'original_uuid': UUID}}
    """
    # There may be multiple mount points inside of the root (/) mount, so
    # iterate over mtab to find all non-special mounts.
    with open('/etc/mtab', 'r') as mounts:
        return {items[1]: {'original_uuid': uuidFromDev(items[0])} for items in
                [mount_line.strip('\n').split(' ')[:2] for mount_line in mounts]
                if uuidFromDev(items[0]) != None}

def wrapLine(msg, size=950, delimiters='\t ', new_line_indicator = 'CONTINUE: '):
    """
    Wrap line ``msg`` into multiple lines with each shorter than ``size``. Try
    to break the line on ``delimiters``. New lines will start with
    ``new_line_indicator``.

    Args:
        msg (str):                  string that should get wrapped
        size (int):                 maximum lenght of returned strings
        delimiters (str):           try to break ``msg`` on these characters
        new_line_indicator (str):   start new lines with this string

    Yields:
        str:                        lines with max ``size`` lenght
    """
    if len(new_line_indicator) >= size - 1:
        new_line_indicator = ''
    while msg:
        if len(msg) <= size:
            yield(msg)
            break
        else:
            line = ''
            for look in range(size-1, size//2, -1):
                if msg[look] in delimiters:
                    line, msg = msg[:look+1], new_line_indicator + msg[look+1:]
                    break
            if not line:
                line, msg = msg[:size], new_line_indicator + msg[size:]
            yield(line)

def syncfs():
    """
    Sync any data buffered in memory to disk.

    Returns:
        bool:   ``True`` if successful
    """
    if checkCommand('sync'):
        return(Execute(['sync']).run() == 0)

def isRoot():
    """
    Check if we are root.

    Returns:
        bool:   ``True`` if we are root
    """
    return os.geteuid() == 0

def usingSudo():
    """
    Check if 'sudo' was used to start this process.

    Returns:
        bool:   ``True`` if process was started with sudo
    """
    return isRoot() and os.getenv('HOME', '/root') != '/root'

re_wildcard = re.compile(r'(?:\[|\]|\?)')
re_asterisk = re.compile(r'\*')
re_separate_asterisk = re.compile(r'(?:^\*+[^/\*]|[^/\*]\*+[^/\*]|[^/\*]\*+|\*+[^/\*]|[^/\*]\*+$)')

def patternHasNotEncryptableWildcard(pattern):
    """
    Check if ``pattern`` has wildcards ``[ ] ? *``.
    but return ``False`` for ``foo/*``, ``foo/*/bar``, ``*/bar`` or ``**/bar``

    Args:
        pattern (str):  path or pattern to check

    Returns:
        bool:           ``True`` if ``pattern`` has wildcards ``[ ] ? *`` but
                        ``False`` if wildcard look like
                        ``foo/*``, ``foo/*/bar``, ``*/bar`` or ``**/bar``
    """
    if not re_wildcard.search(pattern) is None:
        return True

    if not re_asterisk is None and not re_separate_asterisk.search(pattern) is None:
        return True
    return False

BIT_TIME_FORMAT = '%Y%m%d %H%M'
ANACRON_TIME_FORMAT = '%Y%m%d'

def readTimeStamp(fname):
    """
    Read date string from file ``fname`` and try to return datetime.

    Args:
        fname (str):        full path to timestamp file

    Returns:
        datetime.datetime:  date from timestamp file
    """
    if not os.path.exists(fname):
        logger.debug("no timestamp in '%(file)s'" %
                     {'file': fname})
        return
    with open(fname, 'r') as f:
        s = f.read().strip('\n')
    for i in (ANACRON_TIME_FORMAT, BIT_TIME_FORMAT):
        try:
            stamp = datetime.strptime(s, i)
            logger.debug("read timestamp '%(time)s' from file '%(file)s'" %
                         {'time': stamp,
                          'file': fname})
            return stamp
        except ValueError:
            pass

def writeTimeStamp(fname):
    """
    Write current date and time into file ``fname``.

    Args:
        fname (str):        full path to timestamp file
    """
    now = datetime.now().strftime(BIT_TIME_FORMAT)
    logger.debug("write timestamp '%(time)s' into file '%(file)s'" %
                 {'time': now,
                  'file': fname})
    makeDirs(os.path.dirname(fname))
    with open(fname, 'w') as f:
        f.write(now)

INHIBIT_LOGGING_OUT = 1
INHIBIT_USER_SWITCHING = 2
INHIBIT_SUSPENDING = 4
INHIBIT_IDLE = 8

INHIBIT_DBUS = (
               {'service':      'org.gnome.SessionManager',
                'objectPath':   '/org/gnome/SessionManager',
                'methodSet':    'Inhibit',
                'methodUnSet':  'Uninhibit',
                'interface':    'org.gnome.SessionManager',
                'arguments':    (0, 1, 2, 3)
               },
               {'service':      'org.mate.SessionManager',
                'objectPath':   '/org/mate/SessionManager',
                'methodSet':    'Inhibit',
                'methodUnSet':  'Uninhibit',
                'interface':    'org.mate.SessionManager',
                'arguments':    (0, 1, 2, 3)
               },
               {'service':      'org.freedesktop.PowerManagement',
                'objectPath':   '/org/freedesktop/PowerManagement/Inhibit',
                'methodSet':    'Inhibit',
                'methodUnSet':  'UnInhibit',
                'interface':    'org.freedesktop.PowerManagement.Inhibit',
                'arguments':    (0, 2)
               })

def inhibitSuspend(app_id = sys.argv[0],
                    toplevel_xid = None,
                    reason = 'take snapshot',
                    flags = INHIBIT_SUSPENDING | INHIBIT_IDLE):
    """
    Prevent machine to go to suspend or hibernate.
    Returns the inhibit cookie which is used to end the inhibitor.
    """
    if ON_TRAVIS or dbus is None:
        # no suspend on travis (no dbus either)
        return
    if not app_id:
        app_id = 'backintime'
    try:
        if not toplevel_xid:
            toplevel_xid = 0
    except IndexError:
        toplevel_xid = 0

    for dbus_props in INHIBIT_DBUS:
        try:
            #connect directly to the socket instead of dbus.SessionBus because
            #the dbus.SessionBus was initiated before we loaded the environ
            #variables and might not work
            if 'DBUS_SESSION_BUS_ADDRESS' in os.environ:
                bus = dbus.bus.BusConnection(os.environ['DBUS_SESSION_BUS_ADDRESS'])
            else:
                bus = dbus.SessionBus()
            interface = bus.get_object(dbus_props['service'], dbus_props['objectPath'])
            proxy = interface.get_dbus_method(dbus_props['methodSet'], dbus_props['interface'])
            cookie = proxy(*[(app_id, dbus.UInt32(toplevel_xid), reason, dbus.UInt32(flags))[i] for i in dbus_props['arguments']])
            logger.debug('Inhibit Suspend started. Reason: {}'.format(reason))
            return (cookie, bus, dbus_props)
        except dbus.exceptions.DBusException:
            pass
    if isRoot():
        logger.debug("Inhibit Suspend failed because BIT was started as root.")
        return
    logger.warning('Inhibit Suspend failed.')

def unInhibitSuspend(cookie, bus, dbus_props):
    """
    Release inhibit.
    """
    assert isinstance(cookie, int), 'cookie is not int type: %s' % cookie
    assert isinstance(bus, dbus.bus.BusConnection), 'bus is not dbus.bus.BusConnection type: %s' % bus
    assert isinstance(dbus_props, dict), 'dbus_props is not dict type: %s' % dbus_props
    try:
        interface = bus.get_object(dbus_props['service'], dbus_props['objectPath'])
        proxy = interface.get_dbus_method(dbus_props['methodUnSet'], dbus_props['interface'])
        proxy(cookie)
        logger.debug('Release inhibit Suspend')
        return None
    except dbus.exceptions.DBusException:
        logger.warning('Release inhibit Suspend failed.')
        return (cookie, bus, dbus_props)

def readCrontab():
    """
    Read users crontab.

    Returns:
        list:   crontab lines
    """
    cmd = ['crontab', '-l']
    if not checkCommand(cmd[0]):
        logger.debug('crontab not found.')
        return []
    else:
        proc = subprocess.Popen(cmd,
                                stdout = subprocess.PIPE,
                                stderr = subprocess.PIPE,
                                universal_newlines = True)
        out, err = proc.communicate()
        if proc.returncode or err:
            logger.error('Failed to get crontab lines: %s, %s'
                         %(proc.returncode, err))
            return []
        else:
            crontab = [x.strip() for x in out.strip('\n').split('\n')]
            if crontab == ['']:  # Fixes issue #1181 (line count of empty crontab was 1 instead of 0)
                crontab = []
            logger.debug('Read %s lines from users crontab'
                         %len(crontab))
            return crontab

def writeCrontab(lines):
    """
    Write to users crontab.

    Note:
        This will overwrite the whole crontab. So to keep the old crontab and
        only add new entries you need to read it first with
        :py:func:`tools.readCrontab`, append new entries to the list and write
        it back.

    Args:
        lines (:py:class:`list`, :py:class:`tuple`):
                    lines that should be written to crontab

    Returns:
        bool:       ``True`` if successful
    """
    assert isinstance(lines, (list, tuple)), 'lines is not list or tuple type: %s' % lines
    with tempfile.NamedTemporaryFile(mode = 'wt') as f:
        f.write('\n'.join(lines))
        f.write('\n\n')
        f.flush()
        cmd = ['crontab', f.name]
        proc = subprocess.Popen(cmd,
                                stdout = subprocess.DEVNULL,
                                stderr = subprocess.PIPE,
                                universal_newlines = True)
        out, err = proc.communicate()
    if proc.returncode or err:
        logger.error('Failed to write lines to crontab: %s, %s'
                     %(proc.returncode, err))
        return False
    else:
        logger.debug('Wrote %s lines to users crontab'
                     %len(lines))
        return True

def splitCommands(cmds, head = '', tail = '', maxLength = 0):
    """
    Split a list of commands ``cmds`` into multiple commands with each length
    lower than ``maxLength``.

    Args:
        cmds (list):            commands
        head (str):             command that need to run first on every
                                iteration of ``cmds``
        tail (str):             command that need to run after every iteration
                                of ``cmds``
        maxLength (int):        maximum length a command could be.
                                Don't split if <= 0

    Yields:
        str:                    new command with length < ``maxLength``

    Example::

        head cmds[0] cmds[n] tail
    """
    while cmds:
        s = head
        while cmds and ((len(s + cmds[0] + tail) <= maxLength) or maxLength <= 0):
            s += cmds.pop(0)
        s += tail
        yield s

def isIPv6Address(address):
    """
    Check if ``address`` is a valid IPv6 address.

    Args:
        address (str):  address that should get tested

    Returns:
        bool:           True if ``address`` is a valid IPv6 address
    """
    try:
        return isinstance(ipaddress.IPv6Address(address), ipaddress.IPv6Address)
    except:
        return False

def escapeIPv6Address(address):
    """
    Escape IPv6 Addresses with square brackets ``[]``.

    Args:
        address (str):  address that should be escaped

    Returns:
        str:            ``address`` in square brackets
    """
    if isIPv6Address(address):
        return '[{}]'.format(address)
    else:
        return address

def camelCase(s):
    """
    Remove underlines and make every first char uppercase.

    Args:
        s (str):    string separated by underlines (foo_bar)

    Returns:
        str:        string without underlines but uppercase chars (FooBar)
    """
    return ''.join([x.capitalize() for x in s.split('_')])

def fdDup(old, new_fd, mode = 'w'):
    """
    Duplicate file descriptor `old` to `new_fd` and closing the latter first.
    Used to redirect stdin, stdout and stderr from daemonized threads.

    Args:
        old (str):                  Path to the old file (e.g. /dev/stdout)
        new_fd (_io.TextIOWrapper): file object for the new file
        mode (str):                 mode in which the old file should be opened
    """
    try:
        fd = open(old, mode)
        os.dup2(fd.fileno(), new_fd.fileno())
    except OSError as e:
        logger.debug('Failed to redirect {}: {}'.format(old, str(e)))

class UniquenessSet:
    """
    Check for uniqueness or equality of files.

    Args:
        dc (bool):              if ``True`` use deep check which will compare
                                files md5sums if they are of same size but no
                                hardlinks (don't have the same inode).
                                If ``False`` use files size and mtime
        follow_symlink (bool):  if ``True`` check symlinks target instead of the
                                link
        list_equal_to (str):    full path to file. If not empty only return
                                equal files to the given path instead of
                                unique files.
    """
    def __init__(self, dc = False, follow_symlink = False, list_equal_to = ''):
        self.deep_check = dc
        self.follow_sym = follow_symlink
        self._uniq_dict = {}      # if not self._uniq_dict[size] -> size already checked with md5sum
        self._size_inode = set()  # if (size,inode) in self._size_inode -> path is a hlink
        self.list_equal_to = list_equal_to
        if list_equal_to:
            st = os.stat(list_equal_to)
            if self.deep_check:
                self.reference = (st.st_size, md5sum(list_equal_to))
            else:
                self.reference = (st.st_size, int(st.st_mtime))

    def check(self, input_path):
        """
        Check file ``input_path`` for either uniqueness or equality
        (depending on ``list_equal_to`` from constructor).

        Args:
            input_path (str):   full path to file

        Returns:
            bool:               ``True`` if file is unique and ``list_equal_to``
                                is empty.
                                Or ``True`` if file is equal to file in
                                ``list_equal_to``
        """
        # follow symlinks ?
        path = input_path
        if self.follow_sym and os.path.islink(input_path):
            path = os.readlink(input_path)

        if self.list_equal_to:
            return self.checkEqual(path)
        else:
            return self.checkUnique(path)

    def checkUnique(self, path):
        """
        Check file ``path`` for uniqueness and store a unique key for ``path``.

        Args:
            path (str): full path to file

        Returns:
            bool:       ``True`` if file is unique
        """
        # check
        if self.deep_check:
            dum = os.stat(path)
            size,inode  = dum.st_size, dum.st_ino
            # is it a hlink ?
            if (size, inode) in self._size_inode:
                logger.debug("[deep test] : skip, it's a duplicate (size, inode)", self)
                return False
            self._size_inode.add((size,inode))
            if size not in self._uniq_dict:
                # first item of that size
                unique_key = size
                logger.debug("[deep test] : store current size ?", self)
            else:
                prev = self._uniq_dict[size]
                if prev:
                    # store md5sum instead of previously stored size
                    md5sum_prev = md5sum(prev)
                    self._uniq_dict[size] = None
                    self._uniq_dict[md5sum_prev] = prev
                    logger.debug("[deep test] : size duplicate, remove the size, store prev md5sum", self)
                unique_key = md5sum(path)
                logger.debug("[deep test] : store current md5sum ?", self)
        else:
            # store a tuple of (size, modification time)
            obj  = os.stat(path)
            unique_key = (obj.st_size, int(obj.st_mtime))
        # store if not already present, then return True
        if unique_key not in self._uniq_dict:
            logger.debug(" >> ok, store !", self)
            self._uniq_dict[unique_key] = path
            return True
        logger.debug(" >> skip (it's a duplicate)", self)
        return False

    def checkEqual(self, path):
        """
        Check if ``path`` is equal to the file in ``list_equal_to`` from
        constructor.

        Args:
            path (str): full path to file

        Returns:
            bool:       ``True`` if file is equal
        """
        st = os.stat(path)
        if self.deep_check:
            if self.reference[0] == st.st_size:
                return self.reference[1] == md5sum(path)
            return False
        else:
            return self.reference == (st.st_size, int(st.st_mtime))

class Alarm(object):
    """
    Timeout for FIFO. This does not work with threading.
    """
    def __init__(self, callback = None, overwrite = True):
        self.callback = callback
        self.ticking = False
        self.overwrite = overwrite

    def start(self, timeout):
        """
        Start timer
        """
        if self.ticking and not self.overwrite:
            return
        try:
            signal.signal(signal.SIGALRM, self.handler)
            signal.alarm(timeout)
        except ValueError:
            pass
        self.ticking = True

    def stop(self):
        """
        Stop timer before it come to an end
        """
        try:
            signal.alarm(0)
            self.ticking = False
        except:
            pass

    def handler(self, signum, frame):
        """
        Timeout occur.
        """
        self.ticking = False
        if self.callback is None:
            raise Timeout()
        else:
            self.callback()

class ShutDown(object):
    """
    Shutdown the system after the current snapshot has finished.
    This should work for KDE, Gnome, Unity, Cinnamon, XFCE, Mate and E17.
    """
    DBUS_SHUTDOWN ={'gnome':   {'bus':          'sessionbus',
                                'service':      'org.gnome.SessionManager',
                                'objectPath':   '/org/gnome/SessionManager',
                                'method':       'Shutdown',
                                    #methods    Shutdown
                                    #           Reboot
                                    #           Logout
                                'interface':    'org.gnome.SessionManager',
                                'arguments':    ()
                                    #arg (only with Logout)
                                    #           0 normal
                                    #           1 no confirm
                                    #           2 force
                               },
                    'kde':     {'bus':          'sessionbus',
                                'service':      'org.kde.ksmserver',
                                'objectPath':   '/KSMServer',
                                'method':       'logout',
                                'interface':    'org.kde.KSMServerInterface',
                                'arguments':    (-1, 2, -1)
                                    #1st arg   -1 confirm
                                    #           0 no confirm
                                    #2nd arg   -1 full dialog with default logout
                                    #           0 logout
                                    #           1 restart
                                    #           2 shutdown
                                    #3rd arg   -1 wait 30sec
                                    #           2 immediately
                               },
                    'xfce':    {'bus':          'sessionbus',
                                'service':      'org.xfce.SessionManager',
                                'objectPath':   '/org/xfce/SessionManager',
                                'method':       'Shutdown',
                                    #methods    Shutdown
                                    #           Restart
                                    #           Suspend (no args)
                                    #           Hibernate (no args)
                                    #           Logout (two args)
                                'interface':    'org.xfce.Session.Manager',
                                'arguments':    (True,)
                                    #arg        True    allow saving
                                    #           False   don't allow saving
                                    #1nd arg (only with Logout)
                                    #           True    show dialog
                                    #           False   don't show dialog
                                    #2nd arg (only with Logout)
                                    #           True    allow saving
                                    #           False   don't allow saving
                               },
                    'mate':    {'bus':          'sessionbus',
                                'service':      'org.mate.SessionManager',
                                'objectPath':   '/org/mate/SessionManager',
                                'method':       'Shutdown',
                                    #methods    Shutdown
                                    #           Logout
                                'interface':    'org.mate.SessionManager',
                                'arguments':    ()
                                    #arg (only with Logout)
                                    #           0 normal
                                    #           1 no confirm
                                    #           2 force
                               },
                    'e17':     {'bus':          'sessionbus',
                                'service':      'org.enlightenment.Remote.service',
                                'objectPath':   '/org/enlightenment/Remote/RemoteObject',
                                'method':       'Halt',
                                    #methods    Halt -> Shutdown
                                    #           Reboot
                                    #           Logout
                                    #           Suspend
                                    #           Hibernate
                                'interface':    'org.enlightenment.Remote.Core',
                                'arguments':    ()
                               },
                    'e19':     {'bus':          'sessionbus',
                                'service':      'org.enlightenment.wm.service',
                                'objectPath':   '/org/enlightenment/wm/RemoteObject',
                                'method':       'Shutdown',
                                    #methods    Shutdown
                                    #           Restart
                                'interface':    'org.enlightenment.wm.Core',
                                'arguments':    ()
                               },
                    'z_freed': {'bus':          'systembus',
                                'service':      'org.freedesktop.login1',
                                'objectPath':   '/org/freedesktop/login1',
                                'method':       'PowerOff',
                                'interface':    'org.freedesktop.login1.Manager',
                                'arguments':    (True,)
                               }
                   }

    def __init__(self):
        self.is_root = isRoot()
        if self.is_root:
            self.proxy, self.args = None, None
        else:
            self.proxy, self.args = self._prepair()
        self.activate_shutdown = False
        self.started = False

    def _prepair(self):
        """
        Try to connect to the given dbus services. If successful it will
        return a callable dbus proxy and those arguments.
        """
        try:
            if 'DBUS_SESSION_BUS_ADDRESS' in os.environ:
                sessionbus = dbus.bus.BusConnection(os.environ['DBUS_SESSION_BUS_ADDRESS'])
            else:
                sessionbus = dbus.SessionBus()
            systembus  = dbus.SystemBus()
        except:
            return((None, None))
        des = list(self.DBUS_SHUTDOWN.keys())
        des.sort()
        for de in des:
            if de == 'gnome' and self.unity7():
                continue
            dbus_props = self.DBUS_SHUTDOWN[de]
            try:
                if dbus_props['bus'] == 'sessionbus':
                    bus = sessionbus
                else:
                    bus = systembus
                interface = bus.get_object(dbus_props['service'], dbus_props['objectPath'])
                proxy = interface.get_dbus_method(dbus_props['method'], dbus_props['interface'])
                return((proxy, dbus_props['arguments']))
            except dbus.exceptions.DBusException:
                continue
        return((None, None))

    def canShutdown(self):
        """
        Indicate if a valid dbus service is available to shutdown system.
        """
        return(not self.proxy is None or self.is_root)

    def askBeforeQuit(self):
        """
        Indicate if ShutDown is ready to fire and so the application
        shouldn't be closed.
        """
        return(self.activate_shutdown and not self.started)

    def shutdown(self):
        """
        Run 'shutdown -h now' if we are root or
        call the dbus proxy to start the shutdown.
        """
        if not self.activate_shutdown:
            return(False)
        if self.is_root:
            syncfs()
            self.started = True
            proc = subprocess.Popen(['shutdown', '-h', 'now'])
            proc.communicate()
            return proc.returncode
        if self.proxy is None:
            return(False)
        else:
            syncfs()
            self.started = True
            return(self.proxy(*self.args))

    def unity7(self):
        """
        Unity >= 7.0 doesn't shutdown automatically. It will
        only show shutdown dialog and wait for user input.
        """
        if not checkCommand('unity'):
            return False
        proc = subprocess.Popen(['unity', '--version'],
                                stdout = subprocess.PIPE,
                                universal_newlines = True)
        unity_version = proc.communicate()[0]
        m = re.match(r'unity ([\d\.]+)', unity_version)

        return m and Version(m.group(1)) >= Version('7.0') and processExists('unity-panel-service')

class SetupUdev(object):
    """
    Setup Udev rules for starting BackInTime when a drive get connected.
    This is done by serviceHelper.py script (included in backintime-qt)
    running as root though DBus.
    """
    CONNECTION = 'net.launchpad.backintime.serviceHelper'
    OBJECT = '/UdevRules'
    INTERFACE = 'net.launchpad.backintime.serviceHelper.UdevRules'
    MEMBERS = ('addRule', 'save', 'delete')
    def __init__(self):
        if dbus is None:
            self.isReady = False
            return
        try:
            bus = dbus.SystemBus()
            conn = bus.get_object(SetupUdev.CONNECTION, SetupUdev.OBJECT)
            self.iface = dbus.Interface(conn, SetupUdev.INTERFACE)
        except dbus.exceptions.DBusException as e:
            if e._dbus_error_name in ('org.freedesktop.DBus.Error.NameHasNoOwner',
                                      'org.freedesktop.DBus.Error.ServiceUnknown',
                                      'org.freedesktop.DBus.Error.FileNotFound'):
                conn = None
            else:
                raise
        self.isReady = bool(conn)

    def addRule(self, cmd, uuid):
        """
        Prepair rules in serviceHelper.py
        """
        if not self.isReady:
            return
        try:
            return self.iface.addRule(cmd, uuid)
        except dbus.exceptions.DBusException as e:
            if e._dbus_error_name == 'net.launchpad.backintime.InvalidChar':
                raise InvalidChar(str(e))
            elif e._dbus_error_name == 'net.launchpad.backintime.InvalidCmd':
                raise InvalidCmd(str(e))
            elif e._dbus_error_name == 'net.launchpad.backintime.LimitExceeded':
                raise LimitExceeded(str(e))
            else:
                raise

    def save(self):
        """
        Save rules with serviceHelper.py after authentication
        If no rules where added before this will delete current rule.
        """
        if not self.isReady:
            return
        try:
            return self.iface.save()
        except dbus.exceptions.DBusException as e:
            if e._dbus_error_name == 'com.ubuntu.DeviceDriver.PermissionDeniedByPolicy':
                raise PermissionDeniedByPolicy(str(e))
            else:
                raise

    def clean(self):
        """
        Clean up remote cache
        """
        if not self.isReady:
            return
        self.iface.clean()

class PathHistory(object):
    def __init__(self, path):
        self.history = [path,]
        self.index = 0

    def append(self, path):
        #append path after the current index
        self.history = self.history[:self.index + 1] + [path,]
        self.index = len(self.history) - 1

    def previous(self):
        if self.index == 0:
            return self.history[0]
        try:
            path = self.history[self.index - 1]
        except IndexError:
            return self.history[self.index]
        self.index -= 1
        return path

    def next(self):
        if self.index == len(self.history) - 1:
            return self.history[-1]
        try:
            path = self.history[self.index + 1]
        except IndexError:
            return self.history[self.index]
        self.index += 1
        return path

    def reset(self, path):
        self.history = [path,]
        self.index = 0

class OrderedSet(MutableSet):
    """
    OrderedSet from Python recipe
    http://code.activestate.com/recipes/576694/
    """
    def __init__(self, iterable=None):
        self.end = end = []
        end += [None, end, end]         # sentinel node for doubly linked list
        self.map = {}                   # key --> [key, prev, next]
        if iterable is not None:
            self |= iterable

    def __len__(self):
        return len(self.map)

    def __contains__(self, key):
        return key in self.map

    def add(self, key):
        if key not in self.map:
            end = self.end
            curr = end[1]
            curr[2] = end[1] = self.map[key] = [key, curr, end]

    def discard(self, key):
        if key in self.map:
            key, prev, next = self.map.pop(key)
            prev[2] = next
            next[1] = prev

    def __iter__(self):
        end = self.end
        curr = end[2]
        while curr is not end:
            yield curr[0]
            curr = curr[2]

    def __reversed__(self):
        end = self.end
        curr = end[1]
        while curr is not end:
            yield curr[0]
            curr = curr[1]

    def pop(self, last=True):
        if not self:
            raise KeyError('set is empty')
        key = self.end[1][0] if last else self.end[2][0]
        self.discard(key)
        return key

    def __repr__(self):
        if not self:
            return '%s()' % (self.__class__.__name__,)
        return '%s(%r)' % (self.__class__.__name__, list(self))

    def __eq__(self, other):
        if isinstance(other, OrderedSet):
            return len(self) == len(other) and list(self) == list(other)
        return set(self) == set(other)

class Execute(object):
    """
    Execute external commands and handle its output.

    Args:

        cmd (:py:class:`str` or :py:class:`list`):
                            command with arguments that should be called.
                            Depending on if this is :py:class:`str` or
                            :py:class:`list` instance the command will be called
                            by either :py:func:`os.system` (deprecated) or
                            :py:class:`subprocess.Popen`
        callback (method):  function which will handle output returned by
                            command
        user_data:          extra arguments which will be forwarded to
                            ``callback`` function
        filters (tuple):    Tuple of functions used to filter messages before
                            sending them to ``callback``
        parent (instance):  instance of the calling method used only to proper
                            format log messages
        conv_str (bool):    convert output to :py:class:`str` if True or keep it
                            as :py:class:`bytes` if False
        join_stderr (bool): join stderr to stdout

    Note:
        Signals SIGTSTP and SIGCONT send to Python main process will be
        forwarded to the command. SIGHUP will kill the process.
    """
    def __init__(self,
                 cmd,
                 callback = None,
                 user_data = None,
                 filters = (),
                 parent = None,
                 conv_str = True,
                 join_stderr = True):
        self.cmd = cmd
        self.callback = callback
        self.user_data = user_data
        self.filters = filters
        self.currentProc = None
        self.conv_str = conv_str
        self.join_stderr = join_stderr
        #we need to forward parent to have the correct class name in debug log
        if parent:
            self.parent = parent
        else:
            self.parent = self

        if isinstance(self.cmd, list):
            self.pausable = True
            self.printable_cmd = ' '.join(self.cmd)
            logger.debug('Call command "%s"' %self.printable_cmd, self.parent, 2)
        else:
            self.pausable = False
            self.printable_cmd = self.cmd
            logger.warning('Call command with old os.system method "%s"' %self.printable_cmd, self.parent, 2)

    def run(self):
        """
        Start the command.

        Returns:
            int:    returncode from command
        """
        ret_val = 0
        out = ''

        #backwards compatibility with old os.system and os.popen calls
        if isinstance(self.cmd, str):
            logger.deprecated(self)
            if self.callback is None:
                ret_val = os.system(self.cmd)
            else:
                pipe = os.popen(self.cmd, 'r')

                while True:
                    line = tempFailureRetry(pipe.readline)
                    if not line:
                        break
                    line = line.strip()
                    for f in self.filters:
                        line = f(line)
                    if not line:
                        continue
                    self.callback(line, self.user_data)

                ret_val = pipe.close()
                if ret_val is None:
                    ret_val = 0

        #new and preferred method using subprocess.Popen
        elif isinstance(self.cmd, (list, tuple)):
            try:
                #register signals for pause, resume and kill
                signal.signal(signal.SIGTSTP, self.pause)
                signal.signal(signal.SIGCONT, self.resume)
                signal.signal(signal.SIGHUP, self.kill)
            except ValueError:
                #signal only work in qt main thread
                pass

            if self.join_stderr:
                stderr = subprocess.STDOUT
            else:
                stderr = subprocess.DEVNULL
            self.currentProc = subprocess.Popen(self.cmd,
                                                stdout = subprocess.PIPE,
                                                stderr = stderr)
            if self.callback:
                for line in self.currentProc.stdout:
                    if self.conv_str:
                        line = line.decode().rstrip('\n')
                    else:
                        line = line.rstrip(b'\n')
                    for f in self.filters:
                        line = f(line)
                    if not line:
                        continue
                    self.callback(line, self.user_data)

            out = self.currentProc.communicate()[0]
            ret_val = self.currentProc.returncode

            try:
                #reset signals to their default
                signal.signal(signal.SIGTSTP, signal.SIG_DFL)
                signal.signal(signal.SIGCONT, signal.SIG_DFL)
                signal.signal(signal.SIGHUP, signal.SIG_DFL)
            except ValueError:
                #signal only work in qt main thread
                pass

        if ret_val != 0:
            msg = 'Command "%s" returns %s%s%s' %(self.printable_cmd, bcolors.WARNING, ret_val, bcolors.ENDC)
            if out:
                msg += ' | %s' %out.decode().strip('\n')
            logger.warning(msg, self.parent, 2)
        else:
            msg = 'Command "%s..." returns %s' %(self.printable_cmd[:min(16, len(self.printable_cmd))], ret_val)
            if out:
                msg += ': %s' %out.decode().strip('\n')
            logger.debug(msg, self.parent, 2)

        return ret_val

    def pause(self, signum, frame):
        """
        Slot which will send ``SIGSTOP`` to the command. Is connected to
        signal ``SIGTSTP``.
        """
        if self.pausable and self.currentProc:
            logger.info('Pause process "%s"' %self.printable_cmd, self.parent, 2)
            return self.currentProc.send_signal(signal.SIGSTOP)

    def resume(self, signum, frame):
        """
        Slot which will send ``SIGCONT`` to the command. Is connected to
        signal ``SIGCONT``.
        """
        if self.pausable and self.currentProc:
            logger.info('Resume process "%s"' %self.printable_cmd, self.parent, 2)
            return self.currentProc.send_signal(signal.SIGCONT)

    def kill(self, signum, frame):
        """
        Slot which will kill the command. Is connected to signal ``SIGHUP``.
        """
        if self.pausable and self.currentProc:
            logger.info('Kill process "%s"' %self.printable_cmd, self.parent, 2)
            return self.currentProc.kill()

class Daemon:
    """
    A generic daemon class.

    Usage: subclass the Daemon class and override the run() method

    Daemon Copyright by Sander Marechal
    License CC BY-SA 3.0
    http://www.jejik.com/articles/2007/02/a_simple_unix_linux_daemon_in_python/
    """
    def __init__(self, pidfile = None, stdin='/dev/null', stdout='/dev/stdout', stderr='/dev/null', umask = 0o022):
        self.stdin = stdin
        self.stdout = stdout
        self.stderr = stderr
        self.pidfile = pidfile
        self.umask = umask
        if pidfile:
            self.appInstance = ApplicationInstance(pidfile, autoExit = False, flock = False)

    def daemonize(self):
        """
        "Converts" the current process into a daemon
        (= process running in the background)
        and sends a SIGTERM signal to the current process.
        This is done via the UNIX double-fork magic, see Stevens'
        "Advanced Programming in the UNIX Environment" for details (ISBN 0201563177)
        and this explanation: https://stackoverflow.com/a/6011298
        """
        try:
            pid = os.fork()
            logger.debug('first fork pid: {}'.format(pid), self)
            if pid > 0:
                # exit first parent
                sys.exit(0)
        except OSError as e:
            logger.error("fork #1 failed: %d (%s)" % (e.errno, str(e)), self)
            sys.exit(1)

        # decouple from parent environment
        logger.debug('decouple from parent environment', self)
        os.chdir("/")
        os.setsid()
        os.umask(self.umask)

        # do second fork
        try:
            pid = os.fork()
            logger.debug('second fork pid: {}'.format(pid), self)
            if pid > 0:
                # exit from second parent
                sys.exit(0)
        except OSError as e:
            logger.error("fork #2 failed: %d (%s)" % (e.errno, str(e)), self)
            sys.exit(1)

        # redirect standard file descriptors
        logger.debug('redirect standard file descriptors', self)

        sys.stdout.flush()
        sys.stderr.flush()
        fdDup(self.stdin, sys.stdin, 'r')
        fdDup(self.stdout, sys.stdout, 'w')
        fdDup(self.stderr, sys.stderr, 'w')

        signal.signal(signal.SIGTERM, self.cleanupHandler)

        if self.pidfile:
            atexit.register(self.appInstance.exitApplication)
            # write pidfile
            logger.debug('write pidfile', self)
            self.appInstance.startApplication()

    def cleanupHandler(self, signum, frame):
        if self.pidfile:
            self.appInstance.exitApplication()
        sys.exit(0)

    def start(self):
        """
        Start the daemon
        """
        # Check for a pidfile to see if the daemon already runs
        if self.pidfile and not self.appInstance.check():
            message = "pidfile %s already exist. Daemon already running?\n"
            logger.error(message % self.pidfile, self)
            sys.exit(1)

        # Start the daemon
        self.daemonize()
        self.run()

    def stop(self):
        """
        Stop the daemon
        """
        if not self.pidfile:
            logger.debug("Unattended daemon can't be stopped. No PID file", self)
            return

        # Get the pid from the pidfile
        pid, procname = self.appInstance.readPidFile()

        if not pid:
            message = "pidfile %s does not exist. Daemon not running?\n"
            logger.error(message % self.pidfile, self)
            return # not an error in a restart

        # Try killing the daemon process
        try:
            while True:
                os.kill(pid, signal.SIGTERM)
                sleep(0.1)
        except OSError as err:
            if err.errno == errno.ESRCH:
                #no such process
                self.appInstance.exitApplication()
            else:
                logger.error(str(err), self)
                sys.exit(1)

    def restart(self):
        """
        Restart the daemon
        """
        self.stop()
        self.start()

    def reload(self):
        """
        send SIGHUP signal to process
        """
        if not self.pidfile:
            logger.debug("Unattended daemon can't be reloaded. No PID file", self)
            return

        # Get the pid from the pidfile
        pid, procname = self.appInstance.readPidFile()

        if not pid:
            message = "pidfile %s does not exist. Daemon not running?\n"
            logger.error(message % self.pidfile, self)
            return

        # Try killing the daemon process
        try:
            os.kill(pid, signal.SIGHUP)
        except OSError as err:
            if err.errno == errno.ESRCH:
                #no such process
                self.appInstance.exitApplication()
            else:
                sys.stderr.write(str(err))
                sys.exit(1)

    def status(self):
        """
        return status
        """
        if not self.pidfile:
            logger.debug("Unattended daemon can't be checked. No PID file", self)
            return
        return not self.appInstance.check()

    def run(self):
        """
        You should override this method when you subclass Daemon. It will be called after the process has been
        daemonized by start() or restart().
        """
        pass

def __logKeyringWarning():
    from time import sleep
    sleep(0.1)
    logger.warning('import keyring failed')

if keyring is None and keyring_warn:
    #delay warning to give logger some time to import
    from threading import Thread
    thread = Thread(target = __logKeyringWarning, args = ())
    thread.start()