How to run a command via AWS SSM with live output

This little technique is a great example of how simple *nix utilities can be (mis)used to accomplish some interesting things:

 (echo "./deploy.sh" && cat && exit && exit) |  \
   aws ssm start-session --target $INSTANCE_ID

This:

1. Echos the command into the shell session once started (echo "./deploy.sh" - obviously whatever command you want to run goes here)
2. Runs cat to capture any output from that command until the command exits
3. n exit calls, where n is the number of shell sessions you’ve got. I have two, because SSM by default runs sh, then I have a Linux profile set up in SSM that runs bash. This will drop you back where you started, in your shell.

This accomplishes the same result as using send-command with the built-in AWS-RunShellScript document (which is what start-session uses under the hood), but shows output of the command in real-time, just like ssh ... -c would, without the need to wait for the SSM command to finish executing before output is visible.