BASH Hacks as First Class Commands

In my new job at Zendesk, I deal with a lot of Ruby projects that leverage bundler for dependency management. Specifically, right now I’m working with SparkleFormation, stack_master, and aws-vault. With that toolset, each command starts with a staggering 43 static characters that don’t change between commands, like this:

aws-vault exec <AWS profile> -- bundle exec stack_master apply \
<region or alias> <stack name> -c <stack_master config file>

That’s way too long to type out every time I need to act on a stack. Initially I tried to solve this by setting an alias in my BASH profile to abstract the stack_master command:

alias sm=”bundle exec stack_master”

One problem with this approach - if you use a command or binary that spawns a new shell (like aws-vault does), your bash_profile is ignored and your aliases don’t work, defeating the entire purpose.

Fortunately this is an easy problem to solve. Because the default PATH is the same for all shells, we can recreate our alias as a script and place it in /usr/local/bin (or any other directory in the default PATH). We can also leverage BASH’s $@ variable, which captures all positional arguments that come after a script is invoked.

#!/bin/bash

bundle exec stack_master “$@”

Once I created /usr/local/bin/sm and populated it with those lines, executing sm behaved exactly as the original alias, but was also compatible with aws-vault.

For those of you using the same toolset of aws-vault, stack_master, and SparkleFormation, I further condensed my command. Note that this only works if your aws-vault profile, region alias, and stack_master config files share the same name.

#!/bin/bash

# Example command for reference
# aws-vault exec dev -- bundle exec stack_master apply dev stack_name -c dev.yml

aws-vault exec $1 -- bundle exec stack_master $2 $1 $3 -c $1.yml

I put the above code in /usr/local/bin/zsm, so now my stack commands are clean and short:

zsm dev apply my_stack

As always, I hope you found this useful.