Please read the whole answer before attempting to run with sudo
Try running sudo /dvtcolorconvert.rb ~/Themes/ObsidianCode.xccolortheme
The sudo command executes the commands which follow it with ‘superuser’ or ‘root’ privileges. This should allow you to execute almost anything from the command line. That said, DON’T DO THIS! If you are running a script on your computer and don’t need it to access core components of your operating system (I’m guessing you’re not since you are invoking the script on something inside your home directory (~/)), then it should be running from your home directory, ie:
~/dvtcolorconvert.rb ~/Themes/ObsidianCode.xccolortheme
Move it to ~/ or a sub directory and execute from there. You should never have permission issues there and there wont be a risk of it accessing or modifying anything critical to your OS.
If you are still having problems you can check the permissions on the file by running ls -l while in the same directory as the ruby script. You will get something like this:
$ ls -l total 13 drwxr-xr-x 4 or019268 Administ 12288 Apr 10 18:14 TestWizard drwxr-xr-x 4 or019268 Administ 4096 Aug 27 12:41 Wizard.Controls drwxr-xr-x 5 or019268 Administ 8192 Sep 5 00:03 Wizard.UI -rw-r--r-- 1 or019268 Administ 1375 Sep 5 00:03 readme.txt
You will notice that the readme.txt file says -rw-r--r-- on the left. This shows the permissions for that file. The 9 characters from the right can be split into groups of 3 characters of ‘rwx’ (read, write, execute). If I want to add execute rights to this file I would execute chmod 755 readme.txt and that permissions portion would become rwxr-xr-x. I can now execute this file if I want to by running ./readme.txt (./ tells the bash to look in the current directory for the intended command rather that search the $PATH variable).
schluchc alludes to looking at the man page for chmod, do this by running man chmod. This is the best way to get documentation on a given command, man <command>