Core Types

In addition to basic types (string, boolean, integer, arrays...), the Dagger API also provides powerful core types which serve as both arguments and return values for Dagger Functions.

note

The types listed on this page are indicative and not exhaustive. For a complete list of supported types and their fields, refer to the Dagger API reference.

The following table lists available types and what they represent:

Type	Description
CacheVolume	A directory whose contents persist across runs
Container	An OCI-compatible container
CurrentModule	The current Dagger module and its context
Engine	The Dagger Engine configuration and state
Directory	A directory (local path or Git reference)
EnvVariable	An environment variable name and value
File	A file
GitRepository	A Git repository
GitRef	A Git reference (tag, branch, or commit)
Host	The Dagger host environment
Module	A Dagger module
Port	A port exposed by a container
Secret	A secret credential like a password, access token or key)
Service	A content-addressed service providing TCP connectivity
Socket	A Unix or TCP/IP socket that can be mounted into a container
Terminal	An interactive terminal session

Each type exposes additional fields. Some of these are discussed below.

Container

The Container type represents the state of an OCI-compatible container. This Container object is not merely a string referencing an image on a remote registry. It is the actual state of a container, managed by the Dagger Engine, and passed to a Dagger Function's code as if it were just another variable.

Some of the Container type's important fields are:

Field	Description
from	Initializes the container from a specified base image
asService	Turns the container into a Service
asTarball	Returns a serialized tarball of the container as a File
export / import	Writes / reads the container as an OCI tarball to / from a file path on the host
publish	Publishes the container image to a registry
stdout / stderr	Returns the output / error stream of the last executed command
withDirectory / withMountedDirectory	Returns the container plus a directory copied / mounted at the given path
withEntrypoint	Returns the container with a custom entrypoint command
withExec	Returns the container after executing a command inside it
withFile / withMountedFile	Returns the container plus a file copied / mounted at the given path
withMountedCache	Returns the container plus a cache volume mounted at the given path
withRegistryAuth	Returns the container with registry authentication configured
withWorkdir	Returns the container configured with a specific working directory
withServiceBinding	Returns the container with runtime dependency on another Service

Directory

The Directory type represents the state of a directory. This could be either a local directory path or a remote Git reference. Some of its important fields are:

Field	Description
dockerBuild	Builds a new Docker container from the directory
entries	Returns a list of files and directories in the directory
export	Writes the contents of the directory to a path on the host
file	Returns a file at the given path as a File
withFile / withFiles	Returns the directory plus the file(s) copied to the given path

File

The File type represents a single file. Some of its important fields are:

Field	Description
contents	Returns the contents of the file
export	Writes the file to a path on the host

Service

The Service type represents a content-addressed service providing TCP connectivity. Some of its important fields are:

Field	Description
endpoint	Returns a URL or host:port pair to reach the service
hostname	Returns a hostname to reach the service
ports	Returns the list of ports provided by the service
up	Creates a tunnel that forwards traffic from the caller's network to the service

Secret

Dagger allows you to utilize confidential information ("secrets") such as passwords, API keys, SSH keys and so on, without exposing those secrets in plaintext logs, writing them into the filesystem of containers you're building, or inserting them into the cache. The Secret type is used to represent these secret values. Some of its important fields are:

Field	Description
name	Returns the name of the secret
plaintext	Returns the plaintext value of the secret

CurrentModule

The CurrentModule type provides capabilities to introspect the Dagger Function's module and interface between the current execution environment and the Dagger API.

Field	Description
source	Returns the directory containing the module's source code
workdir	Loads and returns a directory from the module's working directory, including any changes that may have been made to it during function execution
workdirFile	Loads and returns a file from the module's working directory, including any changes that may have been made to it during function execution