ZIO Process

Getting Started

To use zio-process, add the following line in your build.sbt file:

libraryDependencies += "dev.zio" %% "zio-process" % "0.1.0"

Usage

Build a description of a command:

val command = Command("cat", "file.txt")

command.run will return a handle to the process as RIO[Blocking, Process]. Alternatively, instead of flat-mapping and calling methods on Process, there are convenience methods on Command itself for some common operations:

// Return output as a list of lines: RIO[Blocking, List[String]]
command.lines

// Return output as a stream of lines: ZStream[Blocking, Throwable, String]
// Particularly useful when dealing with large files and so on as to not use an unbounded amount of memory.
command.linesStream

// Return entire output as string: RIO[Blocking, String]
command.string

// Return only the exit code: RIO[Blocking, Int]
command.exitCode

Piping

You can pipe the output of one process as the input to another. For example, if you want to return a list of all running Java process IDs, you can do the following:

for {
  processes     <- Command("ps", "-ef").stream
  javaProcesses <- Command("grep", "java").stdin(ProcessInput.fromStreamChunk(processes)).stream
  processIds    <- Command("awk", "{print $2}").stdin(ProcessInput.fromStreamChunk(javaProcesses)).lines
} yield processIds

Rather than connecting the outputs and inputs manually in this way, you can use the | operator (or its named equivalent, pipe) like so:

(Command("ps", "-ef") | Command("grep", "java") | Command("awk", "{print $2}")).lines

Inheriting I/O

If you'd like to run a process and handle its input/output in the current process, you can inherit its I/O. For example, running the Scala REPL:

Command("scala").inheritIO.exitCode

Providing environment variables

Command("java", "-version").env(Map("JAVA_HOME" -> javaHome)).string

Specifying the working directory

Command("ls").workingDirectory(new File("/")).lines