Meta Commands

Some of the real power in Cmd.io comes from what you can do with meta commands. Meta command are commands that operate on a command. They look like <command>:<metacommand>. Let’s use the :help meta command on our netpoll command from before to see what we can do:

$ ssh alpha.cmd.io netpoll:help
Usage:
  ssh <user>@cmd.io netpoll:[command]

Available Commands:
  :access     Manage command access
  :admins     Manage command admins
  :env        Manage command environment

Use "[command] --help" for help about a meta command.

You can explore :access and :admins on your own. In short, access lets you share a command with others by adding and removing GitHub usernames. They can run it prefixed with your username and a slash. For example, if I shared netpoll with you, you could run it with ssh cmd.io progrium/netpoll. Access also lets you make a command public, letting any user run it, or make it private again.

The difference between access and admins is currently that admins have access to these meta commands just like you. Users with access don’t. A useful dynamic this allows is storing credentials in configuration, and users with just access can use your commands that use those credentials, but aren’t able to see the credential themselves.

However, if there is a way to display the environment in your command, those credentials will be plainly visible. Use at your own risk.

Setting environment variables

Let’s look at the :env meta command:

$ ssh alpha.cmd.io netpoll:env --help
Manage command environment

Usage:
  demo :config [command]

Available Commands:
  set         Manage command environment
  unset       Manage command environment

Use "[command] --help" for help about a meta command.

What this help is not telling you is that running :env without --help will list current configuration values. However if you do that now, there will be no output since there is no configuration. Let’s set configuration on netpoll.

Configuration is exposed to commands as environment variables, so you can usually just think of :config as managing environment variables. If you look back, our netpoll script actually uses a variable if set called TIMEOUT, which defaults to 10. We can change that value by setting TIMEOUT:

$ ssh alpha.cmd.io netpoll:env set TIMEOUT=30
Config updated.
$ ssh alpha.cmd.io netpoll:env
TIMEOUT=30

Now if you use netpoll against a port that’s not accepting connections, it’s going to loop 30 times instead of 10. This will apply to any user that has access to this command.

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