If the input in a function with arity 1, Exile will call that function with a `Collectable` as the argument. The function must *push* input to this collectable. Return value of the function is ignored.
* `exit_timeout` - Duration to wait for external program to exit after completion before raising an error. Defaults to `:infinity`
* `chunk_size` - Size of each iodata chunk emitted by Enumerable stream. When set to `nil` the output is unbuffered and chunk size will be variable. Defaults to 65535
All other options are passed to `Exile.Process.start_link/3`
One should use `Exile.stream!` over `Exile.Process`. stream internally manages this server for you. Use this only if you need more control over the life-cycle OS process.
## Overview
`Exile.Process` is an alternative primitive for Port. It has different interface and approach to running external programs to solve the issues associated with the ports.
### When compared to Port
* it is demand driven. User explicitly has to `read` output of the command and the progress of the external command is controlled using OS pipes. so unlike Port, this never cause memory issues in beam by loading more than we can consume
* it can close stdin of the program explicitly
* does not create zombie process. It always tries to cleanup resources
At high level it makes non-blocking asynchronous system calls to execute and interact with the external program. It completely bypasses beam implementation for the same using NIF. It uses `select()` system call for asynchronous IO. Most of the system calls are non-blocking, so it does not has adverse effect on scheduler. Issues such as "scheduler collapse".
### Obligatory NIF warning
As with any NIF based solution, bugs or issues in Exile implementation can bring down the beam VM. But NIF implementation is comparatively small and mostly uses POSIX system calls, spawned external processes are still completely isolated at OS level and the port issues it tries to solve are critical.
"""
alias Exile.ProcessNif
require Logger
use GenServer
defmacro fork_exec_failure(), do: 125
# delay between exit_check when io is busy (in milliseconds)