package eio

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The standard environment of a process.

All access to the outside world comes from running the event loop, which provides an environment (e.g. an Eio_unix.Stdenv.base).


let () = @@ fun env ->
  Eio.Path.with_open_dir env#fs "/srv/www" @@ fun www ->
  serve_files www

Standard streams

To use these, see Flow.

val stdin : < stdin : _ Flow.source as 'a.. > -> 'a
val stdout : < stdout : _ Flow.sink as 'a.. > -> 'a
val stderr : < stderr : _ Flow.sink as 'a.. > -> 'a

File-system access

To use these, see Path.

val cwd : < cwd : _ Path.t as 'a.. > -> 'a

cwd t is the current working directory of the process (this may change over time if the process does a "chdir" operation, which is not recommended).

val fs : < fs : _ Path.t as 'a.. > -> 'a

fs t is the process's full access to the filesystem.

Paths can be absolute or relative (to the current working directory). Using relative paths with this is similar to using them with cwd, except that this will follow ".." and symlinks to other parts of the filesystem.

fs is useful for handling paths passed in by the user.


To use this, see Net.

val net : < net : _ Net.t as 'a.. > -> 'a

net t gives access to the process's network namespace.


To use this, see Process.

val process_mgr : < process_mgr : _ Process.mgr as 'a.. > -> 'a

process_mgr t allows you to manage child processes.

Domains (using multiple CPU cores)

To use this, see Domain_manager.

val domain_mgr : < domain_mgr : _ Domain_manager.t as 'a.. > -> 'a

domain_mgr t allows running code on other cores.


To use this, see Time.

val clock : < clock : _ Time.clock as 'a.. > -> 'a

clock t is the system clock (used to get the current time and date).

val mono_clock : < mono_clock : _ Time.Mono.t as 'a.. > -> 'a

mono_clock t is a monotonic clock (used for measuring intervals).


val secure_random : < secure_random : _ Flow.source as 'a.. > -> 'a

secure_random t is an infinite source of random bytes suitable for cryptographic purposes.


val debug : < debug : < Debug.t.. > as 'a.. > -> 'a

debug t provides privileged controls for debugging.

val backend_id : < backend_id : string.. > -> string

backend_id t provides the name of the backend being used.

The possible values are the same as the possible values of the "EIO_BACKEND" environment variable used by


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