As always, protect your data with a recent backup, preferably Time Machine, before executing any commands on the command line. Carefully read and understand what a command does before pressing the Return key as you do so entirely at your own risk. Be aware that future OS updates can break scripts and render them unusable.
Reading List bookmarks are stored along with Safari bookmarks in the ~/Library/Safari/Bookmarks.plist property list file. Although Safari has an option to export Safari bookmarks using the GUI, it does not have an option to export those from the Reading List. If all you want is a list of Reading List URLs, you can use Ruby on the command line to do this. First open a Terminal window and download the required Ruby gem, plist, which will install to /Library/Ruby/Gems/2.0.0/gems/plist-3.1.0:
sudo gem install plist
Type in your admin password when prompted. The following command will place a text file named ReadingListURLs.txt on the Desktop:
plutil -convert xml1 -o - ~/Library/Safari/Bookmarks.plist|ruby -rubygems -e 'require "plist";puts Plist.parse_xml(STDIN.read)["Children"].select{|e|e["Title"]=="com.apple.ReadingList"}[0]["Children"].map{|e|e["URLString"]}' > ~/Desktop/ReadingListURLs.txt
If you want a bookmarks HTML file in the Netscape Bookmark file format that you can import into Safari bookmarks, you can use the Python script, readinglistreader.py. The following command will download a zip file from GitHub containing a folder of the ReadingListReader Python library, unzip the folder to the Desktop, remove the zip file, make readinglistreader.py executable by changing the file permission, and place on the Desktop a bookmarks HTML file of the Reading List bookmarks:
cd ~/Desktop; curl -LOJ 'https://github.com/anoved/ReadingListReader/archive/master.zip' && unzip ReadingListReader-master.zip && rm -f ReadingListReader-master.zip && chmod +x ReadingListReader-master/readinglistreader.py && python ReadingListReader-master/readinglistreader.py --show all --sortorder descending --bookmarks > ReadingList.html
For more info on options to specify for readinglistreader.py, read the README.md file in the ReadingListReader-master folder that was unzipped to the Desktop.
To import ReadingList.html, from Safari's menu bar, navigate to File > Import From > Bookmarks HTML File, locate and select the ReadingList.html file and press the Return key, or click the Import button. While in Safari, press the Command-Option-B keys to edit the bookmarks. You can add, delete, rearrange, and create folders and subfolders. To view them in Safari's Sidebar, click the Sidebar button in the toolbar, or navigate to Bookmarks > Show Bookmarks and click the Bookmarks button. In either case, the Reading List bookmarks will be in the Reading List Bookmarks subfolder of a folder named with an ISO 8601 date format. For example: imported 2015-07-23.
Safari 8 (Yosemite): Use bookmarks
Safari 8 (Yosemite): Keep a reading list
https://github.com/anoved/ReadingListReader
https://rubygems.org/gems/plist/versions/3.1.0
http://plist.rubyforge.org
OS X Man Pages PLUTIL(1)
OS X Man Pages curl(1)
OS X Man Pages UNZIP(1L)
OS X Man Pages RM(1)
OS X Man Pages CHMOD(1)
