42 lines
1.1 KiB
Markdown
42 lines
1.1 KiB
Markdown
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---
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layout: "language"
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page_title: "Conditional Expressions - Configuration Language"
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---
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# Conditional Expressions
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A _conditional expression_ uses the value of a bool expression to select one of
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two values.
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The syntax of a conditional expression is as follows:
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```hcl
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condition ? true_val : false_val
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```
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If `condition` is `true` then the result is `true_val`. If `condition` is
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`false` then the result is `false_val`.
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A common use of conditional expressions is to define defaults to replace
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invalid values:
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```
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var.a != "" ? var.a : "default-a"
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```
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If `var.a` is an empty string then the result is `"default-a"`, but otherwise
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it is the actual value of `var.a`.
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## Conditions
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The condition can be any expression that resolves to a boolean value. This will
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usually be an expression that uses the equality, comparison, or logical
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operators.
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## Result Types
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The two result values may be of any type, but they must both
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be of the _same_ type so that Terraform can determine what type the whole
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conditional expression will return without knowing the condition value.
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