Introduction to ZIO Process

ZIO Process is a simple ZIO library for interacting with external processes and command-line programs.

Introduction

ZIO Process is backed by ZIO Streams, enabling you to work with processes that output gigabytes of data without worrying about exceeding memory constraints.

ZIO Process provides a principled way to call out to external programs from within a ZIO application while leveraging ZIO's capabilities like interruptions and offloading blocking operations to a separate thread pool. We don't need to worry about avoiding these common pitfalls as we would if we were to use Java's ProcessBuilder or the scala.sys.process API since it is already taken care of for you.

Key features of the ZIO Process:

• Deep ZIO Integration — Leverages ZIO to handle interruption and offload blocking operations.
• ZIO Streams — ZIO Process is backed by ZIO Streams, which enables us to obtain the command output as streams of bytes or lines. So we can work with processes that output gigabytes of data without worrying about exceeding memory constraints.
• Descriptive Errors — In case of command failure, it has a descriptive category of errors.
• Piping — It has a simple DSL for piping the output of one command as the input of another.
• Blocking Operations

Installation

In order to use this library, we need to add the following line in our build.sbt file:

libraryDependencies += "dev.zio" %% "zio-process" % "0.7.2" 

Example

Here is a simple example of using ZIO Process:

import zio._
import zio.process.Command

import java.io.File

object ZIOProcessExample extends ZIOAppDefault {
  val myApp = for {
    fiber <- Command("dmesg", "--follow").linesStream
      .foreach(Console.printLine(_))
      .fork
    cpuModel <- (Command("cat", "/proc/cpuinfo") |
      Command("grep", "model name") |
      Command("head", "-n", "1") |
      Command("cut", "-d", ":", "-f", "2")).string
    _ <- Console.printLine(s"CPU Model: $cpuModel")
    _ <- (Command("pg_dump", "my_database") > new File("dump.sql")).exitCode
    _ <- fiber.join
  } yield ()

  override def run = myApp
}