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YAML Syntax
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===========
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This page provides a basic overview of correct YAML syntax, which is how Ansible
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playbooks (our configuration management language) are expressed.
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We use YAML because it is easier for humans to read and write than other common
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data formats like XML or JSON. Further, there are libraries available in most
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programming languages for working with YAML.
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You may also wish to read :doc:`playbooks` at the same time to see how this
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is used in practice.
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YAML Basics
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-----------
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For Ansible, nearly every YAML file starts with a list.
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Each item in the list is a list of key/value pairs, commonly
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called a "hash" or a "dictionary". So, we need to know how
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to write lists and dictionaries in YAML.
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There's another small quirk to YAML. All YAML files (regardless of their association with
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Ansible or not) should begin with ``---``. This is part of the YAML
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format and indicates the start of a document.
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All members of a list are lines beginning at the same indentation level starting
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with a ``"- "`` (a dash and a space)::
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---
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# A list of tasty fruits
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- Apple
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- Orange
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- Strawberry
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- Mango
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A dictionary is represented in a simple ``key: value`` form (the colon must be followed by a space)::
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---
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# An employee record
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name: Example Developer
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job: Developer
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skill: Elite
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Dictionaries can also be represented in an abbreviated form if you really want to::
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---
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# An employee record
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{name: Example Developer, job: Developer, skill: Elite}
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.. _truthiness:
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Ansible doesn't really use these too much, but you can also specify a
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boolean value (true/false) in several forms::
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---
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create_key: yes
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needs_agent: no
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knows_oop: True
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likes_emacs: TRUE
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uses_cvs: false
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Let's combine what we learned so far in an arbitrary YAML example. This really
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has nothing to do with Ansible, but will give you a feel for the format::
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---
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# An employee record
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name: Example Developer
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job: Developer
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skill: Elite
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employed: True
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foods:
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- Apple
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- Orange
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- Strawberry
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- Mango
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languages:
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ruby: Elite
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python: Elite
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dotnet: Lame
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That's all you really need to know about YAML to start writing
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`Ansible` playbooks.
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Gotchas
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-------
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While YAML is generally friendly, the following is going to result in a YAML syntax error::
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foo: somebody said I should put a colon here: so I did
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You will want to quote any hash values using colons, like so::
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foo: "somebody said I should put a colon here: so I did"
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And then the colon will be preserved.
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Further, Ansible uses "{{ var }}" for variables. If a value after a colon starts
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with a "{", YAML will think it is a dictionary, so you must quote it, like so::
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foo: "{{ variable }}"
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.. seealso::
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:doc:`playbooks`
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Learn what playbooks can do and how to write/run them.
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`YAMLLint <http://yamllint.com/>`_
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YAML Lint (online) helps you debug YAML syntax if you are having problems
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`Github examples directory <https://github.com/ansible/ansible-examples>`_
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Complete playbook files from the github project source
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`Mailing List <http://groups.google.com/group/ansible-project>`_
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Questions? Help? Ideas? Stop by the list on Google Groups
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`irc.freenode.net <http://irc.freenode.net>`_
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#ansible IRC chat channel
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