Builtin Commands

Cmd.io is about running and managing user commands. Builtin commands let us add and remove user commands. They’re prefixed with cmd-:

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

Available Commands:
  cmd-add             Install a command
  cmd-ls              List installed commands
  cmd-rm              Uninstall a command

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

Installing a command

We can install a command with cmd-add. We can see how with --help:

$ ssh alpha.cmd.io cmd-add --help
Install a command

Usage:
  ssh <user>@cmd.io cmd-add <name> <source>

Although this help could be more helpful, it does at least tell us the arguments to cmd-add. The first, name, is a name you choose for the command. The second, source, is where to get the command. Right now, the only supported sources are public Docker registries like Docker Hub. Let’s use this mysterious Docker image, progrium/welcome:

$ ssh alpha.cmd.io cmd-add demo progrium/welcome
Command installed
$ ssh alpha.cmd.io
Usage:
  ssh <user>@cmd.io [command]

Available Commands:
  cmd-add             Install a command
  cmd-ls              List installed commands
  cmd-rm              Uninstall a command
  demo

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

Although it lacks a description, the command demo is now available. Run it:

$ ssh alpha.cmd.io demo

Hello! This is a cmd.io command. All it does is display this message.
However, cmd.io commands can do lots more. They can pretty much do
anything you can do in a Docker container, except for long-running
processes like daemons.

You can install cmd.io commands from a number of sources, including
anything off Docker Hub. Once you have a command installed, you can
configure it and share access to it. Anybody that has access to your
command can run it from anywhere they have an SSH client.

Ignoring the fact this message is lying to you (Docker Hub is currently the only source for commands), you’ve run your first Cmd.io command!

The container images you install don’t need to be specific to Cmd.io. Pretty much any CLI tool in a container can be installed. Here’s a netcat container we can use to show that cmd.io port 22 is open:

$ ssh alpha.cmd.io cmd-add nc gophernet/netcat
Command installed
$ ssh alpha.cmd.io nc -z -v cmd.io 22
cmd.io (159.203.159.60:22) open

Removing commands

This is pretty straightforward:

$ ssh alpha.cmd.io cmd-rm nc
Command uninstalled

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