71 lines
3.4 KiB
Markdown
71 lines
3.4 KiB
Markdown
---
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layout: "language"
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page_title: "Expressions - Configuration Language"
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description: "An overview of expressions to reference or compute values in Terraform configurations, including types, operators, and functions."
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---
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# Expressions
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> **Hands-on:** Try the [Create Dynamic Expressions](https://learn.hashicorp.com/tutorials/terraform/expressions?in=terraform/configuration-language&utm_source=WEBSITE&utm_medium=WEB_IO&utm_offer=ARTICLE_PAGE&utm_content=DOCS) tutorial on HashiCorp Learn.
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_Expressions_ are used to refer to or compute values within a configuration.
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The simplest expressions are just literal values, like `"hello"` or `5`,
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but the Terraform language also allows more complex expressions such as
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references to data exported by resources, arithmetic, conditional evaluation,
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and a number of built-in functions.
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Expressions can be used in a number of places in the Terraform language,
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but some contexts limit which expression constructs are allowed,
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such as requiring a literal value of a particular type or forbidding
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[references to resource attributes](/docs/language/expressions/references.html#references-to-resource-attributes).
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Each language feature's documentation describes any restrictions it places on
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expressions.
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You can experiment with the behavior of Terraform's expressions from
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the Terraform expression console, by running
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[the `terraform console` command](/docs/cli/commands/console.html).
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The other pages in this section describe the features of Terraform's
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expression syntax.
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- [Types and Values](/docs/language/expressions/types.html)
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documents the data types that Terraform expressions can resolve to, and the
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literal syntaxes for values of those types.
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- [Strings and Templates](/docs/language/expressions/strings.html)
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documents the syntaxes for string literals, including interpolation sequences
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and template directives.
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- [References to Values](/docs/language/expressions/references.html)
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documents how to refer to named values like variables and resource attributes.
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- [Operators](/docs/language/expressions/operators.html)
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documents the arithmetic, comparison, and logical operators.
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- [Function Calls](/docs/language/expressions/function-calls.html)
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documents the syntax for calling Terraform's built-in functions.
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- [Conditional Expressions](/docs/language/expressions/conditionals.html)
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documents the `<CONDITION> ? <TRUE VAL> : <FALSE VAL>` expression, which
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chooses between two values based on a bool condition.
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- [For Expressions](/docs/language/expressions/for.html)
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documents expressions like `[for s in var.list : upper(s)]`, which can
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transform a complex type value into another complex type value.
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- [Splat Expressions](/docs/language/expressions/splat.html)
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documents expressions like `var.list[*].id`, which can extract simpler
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collections from more complicated expressions.
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- [Dynamic Blocks](/docs/language/expressions/dynamic-blocks.html)
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documents a way to create multiple repeatable nested blocks within a resource
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or other construct.
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- [Type Constraints](/docs/language/expressions/type-constraints.html)
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documents the syntax for referring to a type, rather than a value of that
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type. Input variables expect this syntax in their `type` argument.
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- [Version Constraints](/docs/language/expressions/version-constraints.html)
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documents the syntax of special strings that define a set of allowed software
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versions. Terraform uses version constraints in several places.
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