Notes: * If you want torun a command throughthe shell (say you are using `<', `>', `|', etc), you actually want the [shell] module instead. The `command' module is much more secure asit's not affected bythe user's environment. * `creates', `removes', and `chdir' can be specified afterthe command. For instance, if you only want torun a command if a certain filedoesnot exist, use this.