rbenv shell not command

rbenv shell not command

rbenv installed. but rbenv shell not command.
ationtekiMacBook-Air:~ dation$ rbenv versions
system
* 2.0.0-p247 (set by /Users/dation/.ruby-version)
dationtekiMacBook-Air:~ dation$ rbenv version
2.0.0-p247 (set by /Users/dation/.ruby-version)
dationtekiMacBook-Air:~ dation$ rbenv shell
rbenv: no such command `shell'



ationtekiMacBook-Air:~ dation$ ruby -v
ruby 1.8.7 (2012-02-08 patchlevel 358) [universal-darwin12.0]