prx

An Erlang library for Unix process management and system programming tasks.

prx provides:

a safe, beam-friendly interface to system calls and other POSIX operations
simple, reliable OS process management by mapping Erlang processes to a hierarchy of system processes
an interface for privilege separation operations to restrict processes
operations to isolate processes like containers and jails

Build

$ rebar3 compile

Quick Start

prx has two basic operations: fork and exec.

% Spawn a new system process
{ok, Task} = prx:fork(),

% And a child of the process
{ok, Child} = prx:fork(Task).

After fork()'ing, other calls can be made. For example:

UID = prx:getuid(Task),
PID = prx:getpid(Child).

Calling exec() causes the process I/O to be treated as streams of data:

ok = prx:execvp(Child, ["/bin/cat", "-n"]),
prx:stdin(Child, "test\n"),
receive
    {stdout,Child,Stdout} ->
        Stdout
end.

Usage

fork and exec /bin/cat

  {ok, Task} = prx:fork(),
  ok = prx:execvp(Task, ["/bin/cat", "-n"],
  prx:stdin(Task, "test\n"),
  receive {stdout, Task, _} = Out -> Out end.

creating a pipeline of child processes
prx processes can fork child prx processes:

beam
  |-erl_child_setup
  |   `-prx
  |       `-prx

After calling exec, the process tree looks like:

beam
  |-erl_child_setup
  |   `-prx
  |       `-cat

    {ok, Task} = prx:fork(),
    {ok, Child} = prx:fork(Task),
    OSPid = prx:getpid(Child),
    ok = prx:execvp(Child, ["/bin/cat", "-n"],
    prx:stdin(Child, "test\n"),
    receive {stdout, Child, _} = Out -> Out end.

running cat within a containerized namespace

  application:set_env(prx, options, [{exec, "sudo -n"}]),
  {ok, Task} = prx:fork(),
  {ok, Child} = prx:clone(Task, [clone_newnet, clone_newpid, clone_newipc,
      clone_newuts, clone_newns]),
  OSPid = prx:getpid(Child),
  ok = prx:execvp(Child, ["/bin/cat", "-n"],
  prx:stdin(Child, "test\n"),
  receive {stdout, Child, _} = Out -> Out end.

Documentation

https://hexdocs.pm/prx/