> ## Documentation Index
> Fetch the complete documentation index at: https://errand.nuvrel.dev/llms.txt
> Use this file to discover all available pages before exploring further.

# contains

> Check whether a list contains a specific value.

`contains(list, value)` returns `true` if `value` is present in `list`, and `false` otherwise.

## Signature

```
contains(list list, value any) bool
```

## Example

Only run the container build task when the current operating system is one of the supported platforms:

```hcl theme={null}
computed "current_os" {
  expression = os()
}

task "build-image" {
  description = "Build the Docker image"
  condition   = contains(["linux", "darwin"], computed.current_os)
  commands    = ["docker build -t myapp:latest ."]
}
```

On Windows, where the Docker build task requires different setup, the task is skipped automatically.

## Notes

* The comparison is type-sensitive. A string `"1"` and a number `1` are not equal.
* `contains` works on lists, tuples, and sets, not maps. To check map keys, use [`lookup`](/functions/collection/lookup) with a sentinel value.