Having trouble editing Finder settings using defaults write I run the following command:

sudo defaults write ~/Library/Preferences/com.apple.finder.plist ShowHardDrivesOnDesktop -boolean TRUE


in hopes that this will cause system hard drives to show on the desktop, which doesn't happen.  I kill all Finder processes and restart Finder, but no dice.  

I try to open com.apple.finder.plist in Xcode, but it says I do not have permissions to view the file (I was able to before).  Shortly after, I am able to open it, but the file is empty.  The attributes are slowly regenerating.  

What is happening here?  I am looking for a command to toggle the option to show hard drives on the desktop, just as if I checked the box in Finder preferences.
First of all you shouldn't need sudo and it may have caused the permissions issue, and no need to use the full pathname, just:

defaults write com.apple.finder ShowHardDrivesOnDesktop -boolean TRUE


The following works for me, as is, in OS X 10.8.5 and macOS 10.12.5 in both a Standard and Admin Account in Terminal.

defaults write com.apple.finder ShowHardDrivesOnDesktop -boolean TRUE; killall Finder


Using FALSE, in place of TRUE hides the e.g. Macintosh HD on the Desktop.

I'd probably opt to either restore the file from a known good backup or delete the ~/Library/Preferences/com.apple.finder.plist file and then run killall Finder in Terminal, letting it rebuild and should resolve the permissions issue as well.