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https://github.com/asmeurer/prefsync

Tool to seamlessly sync OS X plist files in a way that can be tracked by git
https://github.com/asmeurer/prefsync

Last synced: 10 days ago
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Tool to seamlessly sync OS X plist files in a way that can be tracked by git

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README 

        
prefsync

========



A little tool to help synchronize Mac OS X plist files (used for preferences

for most Mac Apps) seamlessly, in a way that can be tracked by git.



# Background



Quite a few of us on GitHub upload our

[dotfiles](http://en.wikipedia.org/wiki/Configuration_file)

([here are mine](https://github.com/asmeurer/dotfiles)). It's a nice way to

share configuration, track it with git, and with symlinking, it makes for a

nice semi-manual synchronization scheme.



This trick doesn't work so well with Mac OS X preferences. The issue is that

as of Mac OS X 10.4, [plist files](http://en.wikipedia.org/wiki/Plist) are

binary by default, making them very difficult to track with git.



A typical solution to this file is to symlink the plist files to Dropbox---and

as far as I know that works.  But you lose the ability to easily share your

settings, and perhaps most importantly, track them with git.



The good news is that it's actually possible to use binary plist files, and

automatically convert them back and forth to human-readable (and git

trackable) XML, using some tools that come with Mac OS X.



# Usage



    usage: prefsync [-h] [-t THROTTLE_INTERVAL] PREFFILE DEST



For example



    prefsync ~/Library/Preferences/preferencefile.plist preferencefile.xml



The `-t` flag sets the throttle interval for syncing the file, in seconds. The

default is 10 seconds.



# Installing



You can install it with conda using



    conda install -c conda-forge prefsync



Or using pip



    pip install prefsync



Or from the git source



    python setup.py install



Or you can just run it from the checkout, with



    python -m prefsync



Once you install it, use the command `prefsync`.



# How it works



It's actually quite simple. The heavy work is done for us by the operating

system and tools it provides. The main tools are

[plutil](https://developer.apple.com/library/mac/documentation/Darwin/Reference/ManPages/man1/plutil.1.html),

which allows to convert binary plist files to xml plist files and xml plist

files back to binary, and [launchd](http://en.wikipedia.org/wiki/Launchd),

which provides a facility to automatically run a script when a file changes.



There are some catches, though.



First, if you just do this, it will run cyclically forever, because as soon as

the binary file is updated, it will write to the xml version, which will

register as a change, causing it to write the binary plist, and so on.



We get around this by writing a special extended attribute to each file when

it is written, and ignoring files if they have that attribute (so that only

changes by other things will register).  This will break if something somehow

preserves these attributes. In my tests, they don't, but you can easily test

if your program does by running



    xattr -w test:Test test ~/Library/Preferences/preferencefile.plist



then, make a change to the preferences, and see if the atttribute is still there



    xattr ~/Library/Preferences/preferencefile.plist



Second, in Mac OS X 10.9, preferences are cached, meaning that even if a

program is closed and the plist file is written to, it will be overridden with

the original preferences when it is opened again if the cache was not

flushed.



Getting around this is easy: we just call



    defaults read com.reversedns.preference



(where `com.reversedns.preference` is the reverse DNS for the preference file

in question). This flushes the cache.



Finally, it generally doesn't work to update the binary preference file while

a program is running.  You may be able to just close and reopen the program,

but it may write to the preferences when you do that, overwriting the

changes.



Therefore, it is *highly* recommended to track the XML changes in git, so that

if they are overwritten they can be easily recovered.  To force the changes to

be written to the binary, the easiest way is to close the program, make sure

the xml changes are the same (i.e., closing the program didn't cause the

preferences to be written and synced over to the xml), and then touch the xml

file.



Note that the synchronization in each direction may take up to 10 seconds by

default to take place. You can change this by setting the `-t` flag when

running `prefsync`.



# Gotchas



According to

[this page](http://managingosx.wordpress.com/2006/05/10/launchd-gotcha/)

launchd will stop watching a path if it ceases to exist.  You can reset the

process by logging out and logging back in, or by restarting.  You can also

try using `launchctl`, though this may not work reliably.



# TODO



There is currently no easy way to remove a sync. The best way is to open

Lingon and delete the syncs for the preferences you no longer want to sync. Be

sure to delete both `binarytoxml` and `xmltobinary`. You will need to log out

and log back in or restart for changes to take effect.



# Acknowledgments



The Lingon program is invaluable when working with launchd (the older, free

version works just fine).



StackOverflow and Mac OS X Hints helped me debug some of the strangeness

when trying to get this to work.



# License



MIT (see the LICENSE file).