System.Process.Lens.StdStream

This module provides the associated optics and combinators for working with StdStream objects. StdStream consists of four cases, for which we provide prisms and classy variants.

Prisms

_Inherit :: Prism' StdStream ()

A Prism' into the Inherit structure of a StdStream

Examples:

>>> _Inherit # ()
Inherit

_UseHandle :: Prism' StdStream Handle

A Prism' into the UseHandle structure's Handle for a StdStream

Examples:

>>> _UseHandle # System.stdin
UseHandle {handle: <stdin>}

_CreatePipe :: Prism' StdStream ()

A Prism' into the CreatePipe structure of a StdStream

Examples:

>>> _CreatePipe # ()
CreatePipe

_NoStream :: Prism' StdStream ()

A prism into the NoStream structure of a StdStream

Examples:

>>> _NoStream # ()
NoStream

Classy Prisms

class AsInherit a where

Class constraint proving a type has a prism into an Inherit structure. Any StdStream will have a prism into Inherit - it is just an overwrite to Inherit

Methods

_Inherits :: Prism' a ()

Instances

AsInherit StdStream

Defined in System.Process.Lens.StdStream

Methods

_Inherits :: Prism' StdStream ()

class AsUseHandle a where

Class constraint proving a type has a prism into a Handle via a UseHandle structure.

Methods

_UsesHandle :: Prism' a Handle

Instances

AsUseHandle StdStream

Defined in System.Process.Lens.StdStream

Methods

_UsesHandle :: Prism' StdStream Handle

class AsCreatePipe a where

Class constraint proving a type has a prism into a Handle via a UseHandle structure. Any StdStream will have a prism into CreatePipe - it is just an overwrite to CreatePipe

Methods

_CreatesPipe :: Prism' a ()

Instances

AsCreatePipe StdStream

Defined in System.Process.Lens.StdStream

Methods

_CreatesPipe :: Prism' StdStream ()

class AsNoStream a where

Class constraint proving a type has a prism into a Handle via a UseHandle structure. Any StdStream will have a prism into NoStream - it is just an overwrite to NoStream.

Methods

_NoStreams :: Prism' a ()

Instances

AsNoStream StdStream

Defined in System.Process.Lens.StdStream

Methods

_NoStreams :: Prism' StdStream ()

Combinators

usehandleOf :: AsUseHandle a => Handle -> a

Inject a handle into something with a prism into the handle

Examples:

>>> usehandleOf @StdStream System.stdin
UseHandle {handle: <stdin>}

inheriting :: Lens' a StdStream -> a -> a

Given a lens into a StdStream, overwrite to Inherit so that the stream inherits from its parent process

Examples:

>>> inheriting id CreatePipe
Inherit

piping :: Lens' a StdStream -> a -> a

Given a lens into a StdStream, overwrite to CreatePipe.

Examples:

>>> piping id NoStream
CreatePipe

handling :: Lens' a StdStream -> Handle -> a -> a

Given a lens into a StdStream and a handle, set the handle using UseHandle. Note that this is the only really interesting case for anything with a lens into a handle inculding StdStream.

Examples:

>>> handling id System.stdin $ UseHandle System.stdout
UseHandle {handle: <stdin>}

>>> handling id System.stdin NoStream
NoStream

>>> handling id System.stdin Inherit
Inherit

nostreaming :: Lens' a StdStream -> a -> a

Given a lens into a StdStream, set to NoStream

Examples:

>>> nostreaming id Inherit
NoStream