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README.md

Gem Version

MkStack

Merge multiple CloudFormation template files into a single template. Each file may be in either JSON or YAML format.

Get started with template = MkStack::Template.new, or use the command line tool mkstack.

ERB

By default all files are run through an ERB (Embedded RuBy) processor.

<% desc = "awesome" %>

AWSTemplateFormatVersion: "2010-09-09"
Description: My <%= desc %> CloudFormation template

It is safe to leave this enabled. If a file doesn't have any ERB tags it is passed through untouched.

Include

MkStack searches each file for a section named Include, which should be a list of filenames. These function the same as adding the listed files on the command line.

JSON

"Include" : [
  "foo.yaml",
  "bar.json"
]

YAML

Include:
  - foo.yaml
  - bar.json

ERB and Include working together

MkStack uses a single binding for all files. This allows ERB tags defined in one file to be referenced in subsequent files.

foo.yaml

Include:
  - bar.json

<% tags_json = %q{
     "Tags": [
       { "Key" : "application", "Value" : "mkstack" }
     ]
   }
%>

bar.json

{
  "Resources" : {
    "sg": {
      "Type" : "AWS::EC2::SecurityGroup",
      "Properties" : {
        "GroupDescription" : {
             "Fn::Sub" : "Security Group for ${application}"
        }
        <%= tags_json %>
      }
    }
  }
}

Note that foo.yaml is processed before bar.json.

Command line tool

Usage: mkstack [ options ] file1 [ file2... ]
    -h, --help                       Display this message
        --version                    Show version

    -d, --debug                      Show debug messages
    -v, --verbose                    Be verbose
    -q, --quiet                      Only show errors
    -s, --silent                     Don't show any log messages

    -o, --output=FILE                Print final template to FILE
                                     Use '-' for stdout
    -f, --format=FORMAT              Print as FORMAT
                                     Supported formats: json (default), yaml

        --erb, --[no-]erb            Perform ERB processing (default is true)
        --validate                   Call ValidateTemplate after merging

        ---                          Marks end of mkstack options
                                     Remaining arguments are available to ERB as Array argv

Passing arguments to ERB

Any command line arguments following "---" are added to an Array called argv, which can be referenced in your ERB code.

foo.yaml

<% puts "#{argv.class} with #{argv.length} items: #{argv}" %>

$ mkstack foo.yaml --- a 2 test
Array with 3 items: ["a", "2", "test"]