title: Retrieve a list of installed games from the Steam API
body: <p>I'm working on a Steam Roulette program, and I'm trying to create filters. One of the filters I'd like to implement is (if the user data was loaded with SteamWorks), is to return a list of games (preferably in App ID form) that he/she has installed on his computer that I can then compare to my original full list to remove unneeded values; like a filter to get rid of games the user doesn't have installed on his machine from the list of possible games that can be picked.</p>
  
  <p>In case:</p>
  
  <blockquote>
    <p>Steam Roulette was an online trend, in the form of a web application in which the user picks a random game out of his/her Steam library and plays it.</p>
  </blockquote>
  
  <p>Right now, I'm retrieving user details using the Web API using the Steam ID retrieved with <code>SteamUser.GetSteamID().ToString()</code> and feeding it into:</p>
  
  <pre><code>string apiURL = "http://api.steampowered.com/IPlayerService/GetOwnedGames/v0001/?key=" + APIKey + "&amp;steamid=" + id + "&amp;format=json&amp;include_appinfo=1";
  </code></pre>
  
  <p>And reading the returned <code>.json</code> information from there to generate a list of games that the program can pick from.</p>
  
  <hr>
  
  <p>Is there any SteamWorks function I can use to retrieve a list of games that is installed on the computer, as opposed to <em>all</em> the games that the player owns/has, without reading the steam libraries for their respective folders?</p>
  
  <p>If no possible function exist, is there any way to manually (outside the API) get a list of installed games?</p>