Radiant unpack error


Can anyone help installing Radiant - I have tried gems and subversion on
site5 with no luck. I am following the installation guide to the letter
-http://dev.radiantcms.org/radiant/wiki/Installation - but only get
steps in before hitting a problem when unpacking radiant…

-bash-3.00$ radiant --database mysql radiant60
-bash: radiant: command not found

Where am I going wrong??