ExCmd

ExCmd is an Elixir library to run and communicate with external programs with back-pressure.

ExCmd is built around the idea of streaming data through an external program. Think streaming a video through ffmpeg to serve a web request. For example, getting audio out of a stream is as simple as

ExCmd.stream!(~w(ffmpeg -i pipe:0 -f mp3 pipe:1), input: File.stream!("music_video.mkv", [], 65336))
|> Stream.into(File.stream!("music.mp3"))
|> Stream.run()

Overview

ExCmd uses odu middleware to interact with external process. It uses a demand-driven protocol for IO to have back-pressure. ExCmd.stream! is a stream interface for interacting with the command. One should prefer to use this over ExCmd.Process. Use ExCmd.Process if you need more control.

Check documentation for information

Major advantages over port

• Unlike beam ports, ExCmd puts back pressure on the external program
• Proper program termination. No more zombie process
• Ability to close stdin and wait for output (with ports one can not selectively close stdin)
• Stream abstraction

Check out Exile which is an alternative solution based on NIF

Note: ExCmd is still WIP. Expect breaking changes

Installation

1. Install odu v0.2.2 and make sure its in your path
2. Install ExCmd

def deps do
  [
    {:ex_cmd, "~> x.x.x"}
  ]
end