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/

See also: alcove