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diff --git a/docs/templates.md b/docs/templates.md index bfd254630302..8dff28dd1c38 100644 --- a/docs/templates.md +++ b/docs/templates.md @@ -5,6 +5,13 @@ The template file format is based on Go's [templating engine][] in combination with a small extension library called [sprig][] that adds additional template functions. +Go templates can either simply display variables or build more complicated +*pipelines* in which variables are passed to functions for further processing, +or in which conditionals are evaluated for more complex template logic. + +It is recommended that you check out the Golang [documentation][] for the templating +engine in addition to the cherry-picked features listed here. + ## Basic variable interpolation The basic template format uses `{{ .variableName }}` as the interpolation format. @@ -66,7 +73,7 @@ certKeyPath: my-website/cert-key # The following interpolations are possible: -{{ .name | upper }} +{{ .name | upper }} -> DONALD {{ .name | upper | repeat 2 }} @@ -76,6 +83,39 @@ certKeyPath: my-website/cert-key -> Returns content of 'my-website/cert-key' from pass ``` +## Conditionals & ranges + +Some logic is supported in Golang templates and can be used in Kontemplate, too. + +With the following values: + +``` +useKube2IAM: true +servicePorts: + - 8080 + - 9090 +``` + +The following interpolations are possible: + +``` +# Conditionally insert something in the template: +metadata: + annotations: + foo: bar + {{ if .useKube2IAM -}} iam.amazonaws.com/role: my-api {{- end }} +``` + +``` +# Iterate over a list of values +ports: + {{ range .servicePorts }} + - port: {{ . }} + {{ end }} +``` + +Check out the Golang documentation (linked above) for more information about template logic. + ## Caveats Kontemplate does not by itself parse any of the content of the templates, which @@ -86,6 +126,7 @@ You can perform some validation by using `kontemplate apply --dry-run` which will make use of the Dry-Run functionality in `kubectl`. [templating engine]: https://golang.org/pkg/text/template/ +[documentation]: https://golang.org/pkg/text/template/ [sprig]: http://masterminds.github.io/sprig/ [Go documentation]: https://golang.org/pkg/text/template/#hdr-Functions [pass]: https://www.passwordstore.org/ |