Notes: * If you want to run a command through the shell (say you are using `<', `>', `|', etc), you actually want the [shell] module instead. The `command' module is much more secure as it's not affected by the user's environment. * `creates', `removes', and `chdir' can be specified after the command. For instance, if you only want to run a command if a certain file does not exist, use this.