title: define keybinding for dired to run a command ("open ") on the file under the cursor
body: <p>I want to stop using finder in OSX and use dired instead. OSX has a command, "open ", to open any file in the default app from the cli. (Example: "open $the_file"). This works fine with C-! followed by me entering "open " but I'd like to do both those thing with a key combination, say C-0. </p>
  
  <p>How can I create a function that does the equivalent of "C-!" -> "open " in dired when I press C-0 with the cursor over a filepath?</p>
  
  <p>(EDIT: I found a solution, macros!)</p>