Yaml Syntax Cheat Sheet
This page provides a basic overview of correct YAML syntax, which is how Ansibleplaybooks (our configuration management language) are expressed.
Cheat Sheet learn more at rmarkdown.rstudio.com rmarkdown 0.2.50 Updated: 8/14 1. Workflow R Markdown is a format for writing reproducible, dynamic reports with R. Use it to embed R code and results into slideshows, pdfs, html documents, Word files and more. To make a report. // Update an existing resource(s).yaml or.yml. $ rctl apply -f new-gateway.yaml rctl delete - delete a resource. // Delete all numbers for gateway reference gweef506 $ rctl delete numbers -filter '@.metadata.gwRef'gweef506' // Delete a single agent (using delete alias) $ rctl del agent ag3f77f6. This page contains a list of commonly used kubectl commands and flags. Kubectl autocomplete BASH source /.bashrc # add autocomplete permanently to your bash shell. You can also use a shorthand alias for kubectl that also. . template.yaml (see below). skeleton.Rmd (contents of the template). any supporting files 4 Access template in wizard at File New File R Markdown 3 Install the package- name: My Template -template.yaml Write with syntax on the le# to create effect on right (a#er render) Table suggestionsDebug Mode Several functions format R data.
# MyST Cheat Sheet. ``` No syntax highlighting if no language is. Make sure to include this front-matter YAML block at the beginning of your.ipynb or.md.
We use YAML because it is easier for humans to read and write than other commondata formats like XML or JSON. Further, there are libraries available in mostprogramming languages for working with YAML.
You may also wish to read Working with playbooks at the same time to see how thisis used in practice.
YAML Basics¶
For Ansible, nearly every YAML file starts with a list.Each item in the list is a list of key/value pairs, commonlycalled a “hash” or a “dictionary”. So, we need to know howto write lists and dictionaries in YAML.
There’s another small quirk to YAML. All YAML files (regardless of their association with Ansible or not) can optionallybegin with --- and end with .... This is part of the YAML format and indicates the start and end of a document.
All members of a list are lines beginning at the same indentation level starting with a '-' (a dash and a space):
A dictionary is represented in a simple key:value form (the colon must be followed by a space):
More complicated data structures are possible, such as lists of dictionaries, dictionaries whose values are lists or a mix of both:
Dictionaries and lists can also be represented in an abbreviated form if you really want to:
These are called “Flow collections”.
Ansible doesn’t really use these too much, but you can also specify a boolean value (true/false) in several forms:
Use lowercase ‘true’ or ‘false’ for boolean values in dictionaries if you want to be compatible with default yamllint options.
Values can span multiple lines using | or >. Spanning multiple lines using a “Literal Block Scalar” | will include the newlines and any trailing spaces.Using a “Folded Block Scalar” > will fold newlines to spaces; it’s used to make what would otherwise be a very long line easier to read and edit.In either case the indentation will be ignored.Examples are:
While in the above > example all newlines are folded into spaces, there are two ways to enforce a newline to be kept:
Let’s combine what we learned so far in an arbitrary YAML example.This really has nothing to do with Ansible, but will give you a feel for the format:
Yaml Syntax Cheat Sheet Free
That’s all you really need to know about YAML to start writing Ansible playbooks.
Gotchas¶
While you can put just about anything into an unquoted scalar, there are some exceptions.A colon followed by a space (or newline) ':' is an indicator for a mapping.A space followed by the pound sign '#' starts a comment.
Because of this, the following is going to result in a YAML syntax error:
…but this will work:
You will want to quote hash values using colons followed by a space or the end of the line:
…and then the colon will be preserved.
Alternatively, you can use double quotes:
The difference between single quotes and double quotes is that in double quotesyou can use escapes:
The list of allowed escapes can be found in the YAML Specification under “Escape Sequences” (YAML 1.1) or “Escape Characters” (YAML 1.2).
The following is invalid YAML:
Further, Ansible uses “{{ var }}” for variables. If a value after a colon startswith a “{“, YAML will think it is a dictionary, so you must quote it, like so:
If your value starts with a quote the entire value must be quoted, not just part of it. Here are some additional examples of how to properly quote things:
Not valid:
In addition to ' and ' there are a number of characters that are special (or reserved) and cannot be usedas the first character of an unquoted scalar: []{}>|*&!%#`@,.
You should also be aware of ?:-. In YAML, they are allowed at the beginning of a string if a non-spacecharacter follows, but YAML processor implementations differ, so it’s better to use quotes.
In Flow Collections, the rules are a bit more strict:
Boolean conversion is helpful, but this can be a problem when you want a literal yes or other boolean values as a string.In these cases just use quotes:
Yaml Variable Syntax
YAML converts certain strings into floating-point values, such as the string1.0. If you need to specify a version number (in a requirements.yml file, forexample), you will need to quote the value if it looks like a floating-pointvalue:
Yaml Cheat Sheet Pdf
See also
Learn what playbooks can do and how to write/run them.
YAML Lint (online) helps you debug YAML syntax if you are having problems
Complete playbook files from the github project source
A good guide to YAML syntax
Questions? Help? Ideas? Stop by the list on Google Groups
#ansible IRC chat channel and #yaml for YAML specific questions
Yaml Syntax Cheat Sheet Example
The Specification for YAML 1.1, which PyYAML and libyaml are currentlyimplementing
For completeness, YAML 1.2 is the successor of 1.1