lib/command/server/command.js
function getkeys(req, res) {
  var keys = []
    // target command
    , tcmd = req.args[0]
    , def = Constants.MAP[tcmd];
  if(def) {
    keys = def.getKeys(req.args.slice(1));
  }
  res.send(null, keys);
}
function getkeys(req, res) {
  var keys = []
    // target command
    , tcmd = req.args[0]
    , def = Constants.MAP[tcmd];
  if(def) {
    keys = def.getKeys(req.args.slice(1));
  }
  res.send(null, keys);
}
function getkeys ( req , res ) { var keys = [ ] // target command , tcmd = req . args [ 0 ] , def = Constants . MAP [ tcmd ] ; if ( def ) { keys = def . getKeys ( req . args . slice ( 1 ) ) ; } res . send ( null , keys ) ; }
Respond to the GETKEYS subcommand.

Current version redis@2.8.19 does not actually appear to
implement this: `command getkeys get key` results in an error.

Therefore this implementation is a best guess as to the intended
behaviour.

This command cannot fail with an error so we just return an empty list
for target commands that do not accept keys.

Examples:

command getkeys set key val         // ['key']
command getkeys mset k1 v1 k2 v2    // ['k1', 'k2']
command getkeys hset hash field val // ['hash']
Respond to the GETKEYS subcommand .