es run and Shell Interactions

You may want to use es run in combination with shell features such as quotes, variable expansion, and command substitution. The general rule with es run is:

The passed command will be executed exactly as the same as if es run weren't there, except with a different set of environment variables.

Here's a concrete example:

# We'll use this profile for all examples
[applications.server.profiles.dev]
variables.SERVICE1 = "dev"
variables.SERVICE2 = "also-dev"

# These two invocations of `echo` will look exactly the same to the shell
es run server dev -- echo 'hi'
echo 'hi'

These two commands will behave exactly the same. In other words, if you're not sure how your command will be executed, ignore everything up to and including the --, and that's what the shell will see.

This allows you to add es run to any existing shell command without having to mess around with quotes and backslashes. Here's a more complex example where it's handy:

# Note: this is how you escape single quotes in fish. This command may look
# slightly different in other shells.
es run server dev -- psql -c 'select id from products where cost = \'$30\';'

This will pass the exact string select id from products where cost = '$30'; to psql, without any variable expansion or other shell tomfoolery.

If you encounter any scenarios where the executed command does not behave the same as passing it directly to the shell, please file a bug.

Intentional Variable Expansion

By default, there are two ways to handle variable expansion with es run: before invoking es, and not at all:

es run server dev -- echo $SERVICE1 # prints ""
es run server dev -- echo '$SERVICE1' # prints "$SERVICE1"

In the first example, $SERVICE1 is expanded by the shell before es is executed. In the second example, the single quotes prevent the shell from ever expanding $SERVICE1.

If you want a variable to be expanded after exporting the profile before executing the command, e.g. if you want to use a variable defined by your profile, you'll need to manually invoke a subshell:

es run server dev -- fish -c 'echo $SERVICE1' # prints "dev"