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  root

•  package io

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  root

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  io

•  package vigoo

  Definition Classes

  github

•  package prox

  Provides classes to work with system processes in a type safe way.

  Provides classes to work with system processes in a type safe way.

  Overview

  A system process to be started is represented by the Process case class, taking a command and optionally a list of arguments and a working directory:

  import io.github.vigoo.prox._
  import io.github.vigoo.prox.syntax._
  
  val process = Process("echo", List("Hello world"))

  To start the process, we can use the syntax.ProcessOps.start extension method, defined in syntax.ProcessOps, which creates a cats IO operation returning a RunningProcess instance.

  Use the returned value to wait for the process to exit or to send a termination signal to it:

  val program = Blocker[IO].use { blocker =>
    for {
      echo <- Process("echo", List("Hello world")).start(blocker)
      result <- echo.waitForExit()
    } yield result.exitCode
  }
  
  val exitCode = program.unsafeRunSync()

  Redirection

  The syntax.ProcessNodeInputRedirect, syntax.ProcessNodeOutputRedirect and syntax.ProcessNodeErrorRedirect classes define extension methods for processes to redirect their inpout, output and error streams. The target of redirection can be anything that has the matching type class defined for: CanBeProcessInputSource, CanBeProcessOutputTarget and CanBeProcessErrorTarget.

  The three extension methods are syntax.ProcessNodeInputRedirect.<, syntax.ProcessNodeOutputRedirect.> and syntax.ProcessNodeErrorRedirect.redirectErrorTo

  The type system guarantees that each redirection can only happen once for a process.

  Streams

  The library provides type classes to redirect to/from fs2 streams: InputStreamingSource for feeding a stream as a process' input, and OutputStreamingTarget and ErrorStreamingTarget to feed a process' output and error to fs2 pipes.

  Three special wrapper types can be used to modify how the streams are executed when the IO operation is composed:

  • Drain to run the stream with fs2.Stream.CompileOps.drain, having a result of Unit
  • ToVector to run the stream with fs2.Stream.CompileOps.toVector, having a result of Vector
  • Fold to run the stream with fs2.Stream.CompileOps.fold, having a custom fold result

  If none of the above wrappers is used, the default is to use fs2.Stream.CompileOps.drain for fs2.Sink, fs2.Stream.CompileOps.foldMonoid if the pipe's output is a cats.Monoid and fs2.Stream.CompileOps.toVector otherwise.

  Piping

  The syntax.ProcessNodeOutputRedirect class defined two extension methods for piping one process to another: syntax.ProcessNodeOutputRedirect.| for direct piping and syntax.ProcessNodeOutputRedirect.via for piping through a custom fs2 fs2.Pipe.

  The result of the piping operators is a PipedProcess, which can be used exactly as a simple process, but its syntax.ProcessOps.start method returns a tuple of RunningProcess instances.

  Definition Classes

  vigoo

•  object syntax

  Implicit classes for working with simple and piped processes

  Implicit classes for working with simple and piped processes

  All the operations are implemented for both simple Process objects and PipedProcess objects as well. Most of the operations encode information in the types of the processes as well.

  The operations are implemented by various type classes and exposed through extension methods defined in the implicit classes in this object.

  Examples

  Starting simple and piped processes:

  val echoProcess = Process("echo", List("This is an output"))
  val wordCountProcess = Process("wc", List("-w"))
  val combined = echoProcess | wordCountProcess
  
  for {
    echo1 <- Process("echo", List("Hello world")).start
    runningProcs <- combined.start
    (echo2, wordCount) = runningProcs
  } yield ()

  Redirecting input, output and error channels:

  val p1 = Process("echo", List("Hello world")) > (home / "tmp" / "out.txt")
  val p2 = Process("cat") < (home / "something")
  val p3 = Process("make") errorTo (home / "errors.log")

  Piping:

  val echoProcess = Process("echo", List("This is an output"))
  val wordCountProcess = Process("wc", List("-w"))
  val combined1 = echoProcess | wordCountProcess
  
  val customPipe: Pipe[IO, Byte, Byte] = ???
  val combined2 = echoProcess.via(customPipe).to(wordCountProcess)

  Definition Classes

  prox

• ProcessNodeErrorRedirect
• ProcessNodeInputRedirect
• ProcessNodeOutputRedirect
• ProcessOps

io.github.vigoo.prox.syntax

ProcessOps