StdioDefines the service interface for process standard I/O.
When to use
Use to depend on command-line arguments and standard I/O through the Effect environment.
Details
The service provides command-line arguments, sinks for standard output and
standard error, and a stream of standard input bytes. I/O operations can fail
with PlatformError.
export interface Stdio {
readonly [const TypeId: TypeIdString literal type used as the unique brand for the Stdio service.
When to use
Use to type the runtime identifier stored on Stdio service implementations.
Runtime identifier stored on Stdio service implementations.
Details
This marker is part of the runtime representation of Stdio service
implementations.
TypeId]: type TypeId = "~effect/Stdio"String literal type used as the unique brand for the Stdio service.
When to use
Use to type the runtime identifier stored on Stdio service implementations.
Runtime identifier stored on Stdio service implementations.
Details
This marker is part of the runtime representation of Stdio service
implementations.
TypeId
readonly Stdio.args: Effect.Effect<ReadonlyArray<string>>(property) Stdio.args: {
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
toString: () => string;
toJSON: () => unknown;
}
import EffectEffect.interface Effect<out A, out E = never, out R = never>The Effect interface defines a value that lazily describes a workflow or
job. The workflow requires some context R, and may fail with an error of
type E, or succeed with a value of type A.
When to use
Use when you need to represent a lazy, composable workflow that can require
services, fail with a typed error, or succeed with a typed value.
Details
Effect values model resourceful interaction with the outside world,
including synchronous, asynchronous, concurrent, and parallel interaction.
They use a fiber-based concurrency model, with built-in support for
scheduling, fine-grained interruption, structured concurrency, and high
scalability.
To run an Effect value, you need a Runtime, which is a type that is
capable of executing Effect values.
Effect<interface ReadonlyArray<T>ReadonlyArray<string>>
Stdio.stdout(options?: { readonly endOnDone?: boolean | undefined }): Sink.Sink<void, string | Uint8Array, never, PlatformError>stdout(options: | {
readonly endOnDone?: boolean | undefined
}
| undefined
endOnDone?: boolean | undefinedendOnDone?: boolean | undefined
}): import SinkSink.interface Sink<out A, in In = unknown, out L = never, out E = never, out R = never>A Sink<A, In, L, E, R> is used to consume elements produced by a Stream.
You can think of a sink as a function that will consume a variable amount of
In elements (could be 0, 1, or many), might fail with an error of type E,
and will eventually yield a value of type A together with a remainder of
type L (i.e. any leftovers).
Example (Running a sink with a stream)
import { Effect, Sink, Stream } from "effect"
// Create a simple sink that always succeeds with a value
const sink: Sink.Sink<number> = Sink.succeed(42)
// Use the sink to consume a stream
const stream = Stream.make(1, 2, 3)
const program = Stream.run(stream, sink)
Effect.runPromise(program).then(console.log)
// Output: 42
Namespace containing types and interfaces for Sink variance and type relationships.
Sink<void, string | interface Uint8Array<TArrayBuffer extends ArrayBufferLike = ArrayBufferLike>A typed array of 8-bit unsigned integer values. The contents are initialized to 0. If the
requested number of bytes could not be allocated an exception is raised.
Uint8Array, never, class PlatformErrorclass PlatformError {
message: string;
name: string;
stack: string;
cause: unknown;
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
toString: () => string;
toJSON: () => unknown;
_tag: Tag;
reason: BadArgument | SystemError;
}
Tagged error used by platform APIs to report either invalid arguments or
system-level failures.
When to use
Use as the shared error type for platform APIs that expose invalid arguments
and host or operating-system failures through a single Effect error
channel.
Details
The reason field contains the underlying BadArgument or SystemError.
When that reason has a cause, the cause is preserved on the wrapper.
PlatformError>
Stdio.stderr(options?: { readonly endOnDone?: boolean | undefined }): Sink.Sink<void, string | Uint8Array, never, PlatformError>stderr(options: | {
readonly endOnDone?: boolean | undefined
}
| undefined
endOnDone?: boolean | undefinedendOnDone?: boolean | undefined
}): import SinkSink.interface Sink<out A, in In = unknown, out L = never, out E = never, out R = never>A Sink<A, In, L, E, R> is used to consume elements produced by a Stream.
You can think of a sink as a function that will consume a variable amount of
In elements (could be 0, 1, or many), might fail with an error of type E,
and will eventually yield a value of type A together with a remainder of
type L (i.e. any leftovers).
Example (Running a sink with a stream)
import { Effect, Sink, Stream } from "effect"
// Create a simple sink that always succeeds with a value
const sink: Sink.Sink<number> = Sink.succeed(42)
// Use the sink to consume a stream
const stream = Stream.make(1, 2, 3)
const program = Stream.run(stream, sink)
Effect.runPromise(program).then(console.log)
// Output: 42
Namespace containing types and interfaces for Sink variance and type relationships.
Sink<void, string | interface Uint8Array<TArrayBuffer extends ArrayBufferLike = ArrayBufferLike>A typed array of 8-bit unsigned integer values. The contents are initialized to 0. If the
requested number of bytes could not be allocated an exception is raised.
Uint8Array, never, class PlatformErrorclass PlatformError {
message: string;
name: string;
stack: string;
cause: unknown;
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
toString: () => string;
toJSON: () => unknown;
_tag: Tag;
reason: BadArgument | SystemError;
}
Tagged error used by platform APIs to report either invalid arguments or
system-level failures.
When to use
Use as the shared error type for platform APIs that expose invalid arguments
and host or operating-system failures through a single Effect error
channel.
Details
The reason field contains the underlying BadArgument or SystemError.
When that reason has a cause, the cause is preserved on the wrapper.
PlatformError>
readonly Stdio.stdin: Stream.Stream<Uint8Array, PlatformError>(property) Stdio.stdin: {
channel: Channel.Channel<Arr.NonEmptyReadonlyArray<A>, E, void, unknown, unknown, unknown, R>;
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
}
import StreamStream.interface Stream<out A, out E = never, out R = never>A Stream<A, E, R> describes a program that can emit many A values, fail
with E, and require R.
Details
Streams are pull-based with backpressure and emit chunks to amortize effect
evaluation. They support monadic composition and error handling similar to
Effect, adapted for multiple values.
Example (Creating and consuming streams)
import { Console, Effect, Stream } from "effect"
const program = Effect.gen(function*() {
yield* Stream.make(1, 2, 3).pipe(
Stream.map((n) => n * 2),
Stream.runForEach((n) => Console.log(n))
)
})
Effect.runPromise(program)
// Output:
// 2
// 4
// 6
Stream<interface Uint8Array<TArrayBuffer extends ArrayBufferLike = ArrayBufferLike>A typed array of 8-bit unsigned integer values. The contents are initialized to 0. If the
requested number of bytes could not be allocated an exception is raised.
Uint8Array, class PlatformErrorclass PlatformError {
message: string;
name: string;
stack: string;
cause: unknown;
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
toString: () => string;
toJSON: () => unknown;
_tag: Tag;
reason: BadArgument | SystemError;
}
Tagged error used by platform APIs to report either invalid arguments or
system-level failures.
When to use
Use as the shared error type for platform APIs that expose invalid arguments
and host or operating-system failures through a single Effect error
channel.
Details
The reason field contains the underlying BadArgument or SystemError.
When that reason has a cause, the cause is preserved on the wrapper.
PlatformError>
}
/**
* Service tag for process standard I/O.
*
* **When to use**
*
* Use when you need command-line arguments or standard I/O streams supplied by
* an effect's environment.
*
* @see {@link make} for constructing a `Stdio` service directly
* @see {@link layerTest} for a test layer with defaults and overrides
*
* @category services
* @since 4.0.0
*/
export const const Stdio: Context.Service<Stdio, Stdio>const Stdio: {
key: string;
Service: {
args: Effect.Effect<ReadonlyArray<string>>;
stdout: (options?: { readonly endOnDone?: boolean | undefined }) => Sink.Sink<void, string | Uint8Array, never, PlatformError>;
stderr: (options?: { readonly endOnDone?: boolean | undefined }) => Sink.Sink<void, string | Uint8Array, never, PlatformError>;
stdin: Stream.Stream<Uint8Array, PlatformError>;
};
of: (this: void, self: Stdio) => Stdio;
context: (self: Stdio) => Context.Context<Stdio>;
use: (f: (service: Stdio) => Effect.Effect<A, E, R>) => Effect.Effect<A, E, Stdio | R>;
useSync: (f: (service: Stdio) => A) => Effect.Effect<A, never, Stdio>;
Identifier: Identifier;
stack: string | undefined;
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
toString: () => string;
toJSON: () => unknown;
}
Defines the service interface for process standard I/O.
When to use
Use to depend on command-line arguments and standard I/O through the Effect
environment.
Details
The service provides command-line arguments, sinks for standard output and
standard error, and a stream of standard input bytes. I/O operations can fail
with PlatformError.
Service tag for process standard I/O.
When to use
Use when you need command-line arguments or standard I/O streams supplied by
an effect's environment.
Stdio: import ContextContext.interface Service<in out Identifier, in out Shape>Context key with helper methods for working with a service.
Details
context creates a one-service Context, use and useSync retrieve the
service from the current Effect context before applying a function, and of
is a type-level helper for service values.
Example (Defining a service key)
import { Context } from "effect"
// Define an identifier for a database service
const Database = Context.Service<{ query: (sql: string) => string }>(
"Database"
)
// The key can be used to store and retrieve services
const context = Context.make(Database, { query: (sql) => `Result: ${sql}` })
Creates a Context service key.
When to use
Use when you need to define a context service key for a dependency that must
be provided by the surrounding context.
Details
Call Context.Service("Key") for a function-style key, or use the two-stage
form Context.Service<Self, Shape>()("Key") for class-style service
declarations. The returned key can be yielded as an Effect and passed to
Context.make, Context.add, and the Context getter functions.
Gotchas
The string key is the runtime identity of the service. Reusing the same key
string for unrelated services makes them occupy the same slot in a
Context.
Example (Creating service keys)
import { Context } from "effect"
// Create a simple service
const Database = Context.Service<{
query: (sql: string) => string
}>("Database")
// Create a service class
class Config extends Context.Service<Config, {
port: number
}>()("Config") {}
// Use the services to create contexts
const db = Context.make(Database, {
query: (sql) => `Result: ${sql}`
})
const config = Context.make(Config, { port: 8080 })
Namespace containing utility types for Context service keys.
Example (Extracting service types)
import { Context } from "effect"
const Database = Context.Service<{
query: (sql: string) => string
}>("Database")
// Extract service type from a key
type DatabaseService = Context.Service.Shape<typeof Database>
// Extract identifier type from a key
type DatabaseId = Context.Service.Identifier<typeof Database>
Service<Stdio, Stdio> = import ContextContext.const Service: {
<Identifier, Shape = Identifier>(
key: string
): Service<Identifier, Shape>
<Self, Shape>(): <
Identifier extends string,
E,
R = Types.unassigned,
Args extends ReadonlyArray<any> = never
>(
id: Identifier,
options?:
| {
readonly make:
| ((
...args: Args
) => Effect<Shape, E, R>)
| Effect<Shape, E, R>
| undefined
}
| undefined
) => ServiceClass<Self, Identifier, Shape> &
([Types.unassigned] extends [R]
? unknown
: {
readonly make: [Args] extends [never]
? Effect<Shape, E, R>
: (
...args: Args
) => Effect<Shape, E, R>
})
<Self>(): <
Identifier extends string,
Make extends
| Effect<any, any, any>
| ((...args: any) => Effect<any, any, any>)
>(
id: Identifier,
options: { readonly make: Make }
) => ServiceClass<
Self,
Identifier,
Make extends
| Effect<infer _A, infer _E, infer _R>
| ((
...args: infer _Args
) => Effect<infer _A, infer _E, infer _R>)
? _A
: never
> & { readonly make: Make }
}
const TypeId: TypeIdString literal type used as the unique brand for the Stdio service.
When to use
Use to type the runtime identifier stored on Stdio service implementations.
Runtime identifier stored on Stdio service implementations.
Details
This marker is part of the runtime representation of Stdio service
implementations.
TypeId)