Command-Line Utilities in Font

Generate QR Code in Font Command-Line Utilities

Property List Editor is useful for getting your feet wet and very basic tasks. It has some shortcomings, though. Namely, the problem is scalability. If you need to manipulate a .plist file on more than one machine----let s say 500----Property List Editor would be a tedious way to manage. What if you need to update these .plist files from home, all automatically This is what shell scripts and command-line utilities were designed for. There are three command-line tools that ship with Mac OS X: plutil, defaults, and PlistBuddy. Each has a different purpose and different capabilities.

plutil is the most basic and utilitarian of the three. plutil, the .plist utility, converts .plist files between text (XML) and binary formats and can also verify the structure of a .plist file. An example is in order. If you want to view the contents of a binary .plist file----com.apple.nat.plist, for example----but don t want to open it in Property List Editor, you can run the following:

Running this command tells plutil to convert the .plist file to text ( xml1 ) and send the output ( -o ) to standard out. If you wanted to store the file, you could write the output to a file on disk.

plutil can also lint a file----that is, check it for consistency and basic errors. What it cannot do is verify that your key-names and data are correct. Running a lint check is as simple as using the -lint switch:

$ plutil -lint /Library/Preferences/com.apple.loginwindow.plist /Library/Preferences/com.apple.loginwindow.plist: OK

If the lint process encounters an error (or errors, perhaps), you re told the error and on which line:

The defaults command gives you access to the user defaults system. As mentioned, the user defaults system is a fancy way of saying preferences, which, as you know by now, is just data stored in a .plist (for today: Apple reserves the right to change this format). The name is derived from the Cocoa API that performs the same task: NSUserDefaults. The defaults utility allows for reading and writing individual keys and their data to and from a .plist file, reading a .plist file in whole, and more. Perhaps the simplest use of the defaults command is reading an entire .plist file. This is equivalent to the plutil command given earlier:

$ defaults read /Library/Preferences/com.apple.nat { NatPortMapDisabled = 0; }

You ll note that the output of the defaults command is concerned only with keys and their values. It does not output the XML header and closing tags. The defaults command reads .plist files of either XML or binary. However, it will write a .plist file out only in the binary variety. It will even go so far as to convert an XML .plist file into binary if used to update a value in that .plist file. As it's intdended to be used to manage "defaults" (Core Foundation Preferences) and not .plist files, the defaults command is very particular----when you ask it to operate on a specific .plist file, you must give it the absolute path and leave off the .plist extension. This is very unlike most command-line tools that operate on files, and it takes some getting used to. The fact that the defaults command operates on .plist files is a happy coincidence that we can take advantage of.

NOTE: If you re using the defaults command in a script, you should be aware of certain behaviors (in addition to the leave-the-.plist-extension-off-of-the-file-name oddity). First, you shouldn t change the defaults of a running application. If you make a change to a running application, at best, the change won t be recognized. At worst, it may save on exit and wipe out your change or possibly corrupt the .plist file. Secondly, the defaults command does not have a wide range of exit codes: 0 for success and 1 for a failure of any type. If you do not specify an absolute path, defaults looks for a preference domain for the current user. The following command will read the HomeSync preferences for the current user, not a file named com.apple.homeSync or com.apple.homeSync.plist in the current directory.