data_external_command

This module reads an output from a command/script.

Why

Terraform does not provide the possibility (yet) to store custom variables in null_resource, which means that null_resource with local-exec can be used to created/update/delete resources through external commands, but they can not be referenced.

The data "external" module helps to encapsulate and reference not (yet fully) supported resources, but it lacks cross-plattform support. This module is a wrapper which allows you to run a bash script on window and unix.

Usage

module "command" {
  source      = "github.com/octocraft/terraform-module-data_external_command"
  module_path = "${path.module}"
  command     = "jq -n --arg v \"$(echo bar)\" '{\"foo\": $v}'"
}

Variables

module_path

Pass ${path.module} to this variable to access it via $module_path from the shell

command

The command to be executed (bash shell).

jq can be used to filter/modify json data easily. If the command is not available, the version from /bin/$OS/ is used. More Details: https://stedolan.github.io/jq/

The command must return valid JSON. This module uses internally data "external". I.e.

• If you want to pass quotes you have to double escape them \\\"
• Terraform does not execute the program through a shell, so it is not necessary to escape shell metacharacters nor add quotes around arguments containing spaces.

More Details: https://www.terraform.io/docs/providers/external/data_source.html

Sample command

jq -n --arg v "$(echo bar)" '{"foo": $v}'

returns

{
  "foo": "bar"
}

Environment Variables

The module exposes the following variables to the command/script:

$module_path The directory of the module.

$OS The type of the operating system. $OS is set to 'darwin', 'freebsd', 'linux', 'openbsd', 'solaris' or 'windows'.

$OSTYPE On Unix systems $OSTYPE is already set. On Windows this is set to "windows".

Outputs

result

The result returned by the command.

To access keys of the result you have to use lookup

output "foo" {
  value = "${lookup(module.command.result, "foo")}"
}

returns

foo = bar

Notes

This module ships with binaries for all platforms supported by Terraform (Maс OSX, FreeBSD, Linux, OpenBSD, Solaris and Windows), except linux/arm.

It comes with a bash shell for Windows, but it does not ship with any functions (i.e. you will most likely not be able to run many scripts due to dependencies on Unix functions). Also the shell used is quite old (win bash uses bash 1.14.2).

If you are on Windows and you prefer Cygwin you can tweak run.sh.bat to use it instead of bash.exe.

If you don't care about Windows you can safely use any commands which are available on your OS, but please keep in mind, that your code is platform dependent and Terraform may fail in certain environments due to missing dependencies.

License

MIT