scala ammonite script that implement `watch -d ""` that shows only diffs. I was using it to see changes in `lsof -p SOMEPROCID` to watch if there are any leaks in my app.

watchDiff.scala

//> using toolkit latest
//> using dep io.github.java-diff-utils:java-diff-utils:4.12
//> using dep com.lihaoyi::fansi::0.4.0

// use like this: scala-cli run . -- 200 lsof -p 28482

import com.github.difflib.*
import com.github.difflib.patch.*
import fansi.*
import os.*

import java.util.stream.Collectors
import java.util.{ArrayList, Arrays, Date, List as JList}
import scala.collection.mutable.Buffer
import scala.reflect.ClassTag

extension (s: String)
  def linesJList: JList[String] = s.lines().collect(Collectors.toList())

extension [T <: AnyRef: ClassTag](s: JList[T])
  def array: Array[T] = s.toArray[T](new Array[T](s.size()))

def str(p: String, color: EscapeAttr)(target: Array[String]): Array[Str] =
  target.map(s => color(p + ": " + s))

def text(d: AbstractDelta[String]): Array[Str] =
  def target = d.getTarget.getLines.array
  def source = d.getSource.getLines.array

  d match
    case _: InsertDelta[String] => str(" +", Color.Blue)(target)
    case _: ChangeDelta[String] =>
      str("~-", Color.LightYellow)(source) ++ str("~+", Color.LightGreen)(target)
    case _ => str(" -", Color.Red)(source)

@main def lines(time: Int, cmd: String*): Unit =
  def call() = os.proc(cmd).call().toString()

  val initState = call()
  val cmdStr = cmd.mkString(" ")

  while true do
    Thread.sleep(time)
    val newState = call()
    val diffs = DiffUtils.diff(initState.linesJList, newState.linesJList)
    print("\u001b[2J\u001b[;H")
    val cmdLine = s"CMD: ${cmdStr}  TIME:${Date()}"
    println(cmdLine)
    println("-" * cmdLine.length)
    diffs.getDeltas.asScala.flatMap(text).foreach(println)

Example usage:

amm ./watchDiff.scala 200 lsof -p 1119701