fancy_defaults_read.py: Reads a preference, prints its value, type, and where it is defined.

fancy_defaults_read.py

#!/usr/bin/python

import os
import sys

from CoreFoundation import (CFPreferencesAppValueIsForced,
                            CFPreferencesCopyAppValue,
                            CFPreferencesCopyValue,
                            kCFPreferencesAnyUser,
                            kCFPreferencesAnyHost,
                            kCFPreferencesCurrentUser,
                            kCFPreferencesCurrentHost)


def get_type(value):
    '''Returns type of pref value'''
    if value is None:
        return 'null'
    type_name = type(value).__name__
    if type_name == '__NSCFDictionary':
        return 'dictionary'
    if type_name == '__NSCFArray':
        return 'array'
    if type_name in ('pyobjc_unicode', '__NSCFString'):
        return 'string'
    if type_name in ('bool', '__NSCFBoolean'):
        return 'boolean'
    if type_name == '__NSCFData':
        return 'data'
    if type_name == '__NSDate':
        return 'date'
    if type_name == 'OC_PythonLong':
        return 'integer'
    if type_name == 'OC_PythonFloat':
        return 'real'
    return type(value).__name__


def get_config_level(bundle_id, pref_name, value):
    '''Returns a string indicating where the given preference is defined'''
    if value is None:
        return 'not set'
    if CFPreferencesAppValueIsForced(pref_name, bundle_id):
        return 'MANAGED'
    home_dir = os.path.expanduser('~')
    # define all the places we need to search, in priority order
    levels = [
        {'file': os.path.join(home_dir, 'Library/Preferences/ByHost',
                              bundle_id + '.xxxx.plist'),
         'domain': bundle_id,
         'user': kCFPreferencesCurrentUser,
         'host': kCFPreferencesCurrentHost
        },
        {'file': os.path.join(home_dir, 'Library/Preferences/',
                              bundle_id + '.plist'),
         'domain': bundle_id,
         'user': kCFPreferencesCurrentUser,
         'host': kCFPreferencesAnyHost
        },
        {'file': os.path.join(home_dir, 'Library/Preferences/ByHost',
                              '.GlobalPreferences.xxxx.plist'),
         'domain': '.GlobalPreferences',
         'user': kCFPreferencesCurrentUser,
         'host': kCFPreferencesCurrentHost
        },
        {'file': os.path.join(home_dir, 'Library/Preferences',
                              '.GlobalPreferences.plist'),
         'domain': '.GlobalPreferences',
         'user': kCFPreferencesCurrentUser,
         'host': kCFPreferencesAnyHost
        },
        {'file': os.path.join('/Library/Preferences', bundle_id +'.plist'),
         'domain': bundle_id,
         'user': kCFPreferencesAnyUser,
         'host': kCFPreferencesCurrentHost
        },
        {'file': '/Library/Preferences/.GlobalPreferences.plist',
         'domain': '.GlobalPreferences',
         'user': kCFPreferencesAnyUser,
         'host': kCFPreferencesCurrentHost
        },
    ]
    for level in levels:
        if (value == CFPreferencesCopyValue(
                pref_name, level['domain'], level['user'], level['host'])):
            return level['file']
    if value == DEFAULT_PREFS.get(pref_name):
        return 'default'
    return 'unknown'


def get_pref_value(bundle_id, pref_name):
    '''Returns the effective value of a preference'''
    return CFPreferencesCopyAppValue(pref_name, bundle_id)


def main():
    try:
        domain = sys.argv[1]
        key = sys.argv[2]
    except IndexError:
        print >> sys.stderr, "Usage: %s <domain> <key>" % sys.argv[0]
        sys.exit(-1)

    value = get_pref_value(domain, key)
    kind = get_type(value)
    where = get_config_level(domain, key, value)
    print '%s: %s' % (key, repr(value))
    print 'Type: %s' % kind
    print 'Defined: %s' % where


if __name__ == '__main__':
    main()

zzzREADME.txt

Examples of the use of fancy_defaults_read.py:

$ ./fancy_defaults_read.py com.apple.finder AppleShowAllExtensions
AppleShowAllExtensions: False
Type: boolean
Defined: /Users/gneagle/Library/Preferences/com.apple.finder.plist

$ ./fancy_defaults_read.py com.apple.SoftwareUpdate CatalogURL
CatalogURL: u'http://su.mycorp.com/index_testing.sucatalog'
Type: string
Defined: /Library/Preferences/com.apple.SoftwareUpdate.plist

$ ./fancy_defaults_read.py com.apple.screensaver askForPassword
askForPassword: True
Type: boolean
Defined: MANAGED

$ ./fancy_defaults_read.py com.apple.screensaver moduleDict
moduleDict: {
    moduleName = iLifeSlideshows;
    path = "/System/Library/Frameworks/ScreenSaver.framework/Resources/iLifeSlideshows.saver";
    type = 0;
}
Type: dictionary
Defined: /Users/gneagle/Library/Preferences/ByHost/com.apple.screensaver.xxxx.plist

Suggested improvements left for the reader: 

1) Instead of '/Library/Preferences/ByHost/com.apple.screensaver.xxxx.plist', print the actual filename.
2) Add support for sandboxed applications that store their preferences in ~/Library/Containers/<identifier>/Data/Library/Preferences/<identifier>.plist