/usr/libexec/PlistBuddy -c "Set :cust_info:pid 94758476" com.apress.example.plist in Font

Creating QR Code in Font /usr/libexec/PlistBuddy -c "Set :cust_info:pid 94758476" com.apress.example.plist

NOTE: If you run PlistBuddy from a directory other than the one containing the .plist file you re manipulating, you ll need to specify the full path of the .plist file to edit. See the PlistBuddy main page (note the capitalization) for more information on the utility. PlistBuddy is capable of much, much more, including copying values and merging .plist files.

As alluded to earlier in this chapter, Apple s Cocoa framework has native methods for reading and writing property list files. Cocoa is exposed to Python, Ruby, and Perl via the Objective-C bridge. While a full-out course on any of these scripting languages is beyond the scope of this book, we can give an overview for people who have some experience and just need examples of creating, writing, and reading .plist files. Why, though, would you want to use a language like Ruby or Python instead of the other command-line tools (plutil, PlistBuddy, and, particularly, defaults) and bash scripting From time to time, as a system administrator, you ll find yourself in a position where you d like a script to store its own preferences. Or, you d like to simply have a script analyze a .plist file and act on the contents in some manner. In many cases, bash scripting will be perfectly acceptable. However, for anything with a little more complexity, you may already be scripting in Python, Perl, or Ruby. While you can successfully use any of these, for demonstration purposes, we re going to use Python. NOTE: PyObjC is built into OS X 10.5 and above, and only with Python 2.5 and above. It s possible to use PyObjC with 10.4-based machines, but you ll need to compile and install PyObjC yourself. Mac OS X 10.5 ships with both Python 2.4 and 2.5, so be sure to stick with the default version of 2.5. Mac OS X 10.6 ships with both Python 2.5 and 2.6; both contain the Objective-C bridge support. Python, with PyObjC (the Objective-C bridge), turns working with property list files into a pretty trivial operation. Most importantly, you get the best of both worlds: Apple s APIs, along with Python s ease of use and the speed of the edit and run cycle (skipping the compile step of C-based languages). To see this in action, let s start with nearly the simplest example possible. Listing 4-1 contains write_plist.py, which demonstrates creating a dictionary that gets written to a .plist file.

Listing 4-1. write_plist.py #!/usr/bin/python2.5 from Foundation import NSMutableDictionary my_dict = NSMutableDictionary.dictionary() my_dict['color'] = 'blue' my_dict['count'] = 15 my_dict['style'] = 'fruit' success = my_dict.writeToFile_atomically_('com.apress.example.plist', 1) if not success: print "plist failed to write!" sys.exit(1)

Upon running this program, com.apress.example.plist will be created in the same working directory as the program itself. The .plist file will match the output that is shown in Listing 4-1. Let s examine this line by line to see how it works. The very first line----#!/usr/bin/python2.5----is a good reminder that Python version 2.5 or higher is required for PyObjC integration. This will not work on Tiger systems out of the box.

This import is responsible for all of the magic here. While we could import all of Foundation, we ll import just the portion we need: NSMutableDictionary.

my_dict = NSMutableDictionary.dictionary()

Typically, creating a dictionary in Python would use curly braces, like this:

new_dict = {}

Or, you can even fill it on creation:

new_dict = {'color':'blue', 'count':15, 'style':'fruit'}

However, we need to create a real Cocoa NSMutableDictionary object, so that s what we ve done. Nicely, we can now go on and treat that just like a Python dictionary:

my_dict['color'] = 'blue' my_dict['count'] = 15 my_dict['style'] = 'fruit'

You can use the Cocoa API for adding entries to a dictionary as well:

my_dict.setValue_forKey_('stop', 'state')

This would set the key state to store the value stop, and add the following to the .plist file once written out: