diff --git a/src/compiler/scala/tools/nsc/CompilerCommand.scala b/src/compiler/scala/tools/nsc/CompilerCommand.scala
index b2f027de5b24..b895d4438c63 100644
--- a/src/compiler/scala/tools/nsc/CompilerCommand.scala
+++ b/src/compiler/scala/tools/nsc/CompilerCommand.scala
@@ -126,11 +126,11 @@ class CompilerCommand(arguments: List[String], val settings: Settings) {
   def expandArg(arg: String): List[String] = {
     import java.nio.file.{Files, Paths}
     import scala.jdk.CollectionConverters._
-    def stripComment(s: String) = s.takeWhile(_ != '#').trim()
-    val file = Paths.get(arg.stripPrefix("@"))
+    def stripComment(s: String) = s.takeWhile(_ != '#')
+    val file = Paths.get(arg stripPrefix "@")
     if (!Files.exists(file))
       throw new java.io.FileNotFoundException(s"argument file $file could not be found")
-    Files.readAllLines(file).asScala.map(stripComment).filter(_ != "").toList
+    settings.splitParams(Files.readAllLines(file).asScala.map(stripComment).mkString(" "))
   }
 
   // override this if you don't want arguments processed here
diff --git a/src/compiler/scala/tools/nsc/settings/MutableSettings.scala b/src/compiler/scala/tools/nsc/settings/MutableSettings.scala
index 314b5393138f..49e4a8f405b5 100644
--- a/src/compiler/scala/tools/nsc/settings/MutableSettings.scala
+++ b/src/compiler/scala/tools/nsc/settings/MutableSettings.scala
@@ -973,5 +973,5 @@ class MutableSettings(val errorFn: String => Unit, val pathFactory: PathFactory)
 }
 
 private object Optionlike {
-  def unapply(s: String): Boolean = s.startsWith("-") && s != "-"
+  def unapply(s: String): Boolean = s.startsWith("-")
 }
diff --git a/src/library/scala/sys/process/Parser.scala b/src/library/scala/sys/process/Parser.scala
index 19b82c905091..89a2dd56db32 100644
--- a/src/library/scala/sys/process/Parser.scala
+++ b/src/library/scala/sys/process/Parser.scala
@@ -13,8 +13,6 @@
 package scala.sys.process
 
 import scala.annotation.tailrec
-import collection.mutable.ListBuffer
-import Character.isWhitespace
 
 /** A simple enough command line parser using shell quote conventions.
  */
@@ -23,54 +21,87 @@ private[scala] object Parser {
   private final val SQ = '\''
   private final val EOF = -1
 
-  /** Split the line into tokens separated by whitespace.
+  /** Split the line into tokens separated by whitespace or quotes.
    *
-   *  Tokens may be surrounded by quotes and may contain whitespace or escaped quotes.
-   *
-   *  @return list of tokens
+   *  @return either an error message or reverse list of tokens
    */
   def tokenize(line: String, errorFn: String => Unit): List[String] = {
-    val accum = ListBuffer.empty[String]
-    val buf   = new java.lang.StringBuilder
-    var pos   = 0
+    import Character.isWhitespace
+    import java.lang.{StringBuilder => Builder}
+    import collection.mutable.ArrayBuffer
 
-    def cur: Int = if (done) EOF else line.charAt(pos)
-    def bump()   = pos += 1
-    def put()    = { buf.append(cur.toChar); bump() }
-    def done     = pos >= line.length
+    var accum: List[String] = Nil
+    var pos = 0
+    var start = 0
+    val qpos = new ArrayBuffer[Int](16)    // positions of paired quotes
 
-    def skipWhitespace() = while (isWhitespace(cur)) bump()
+    def cur: Int  = if (done) EOF else line.charAt(pos)
+    def bump() = pos += 1
+    def done   = pos >= line.length
 
-    // Collect to end of word, handling quotes. False for missing end quote.
-    def word(): Boolean = {
+    // Skip to the next quote as given.
+    def skipToQuote(q: Int): Boolean = {
+      var escaped = false
+      def terminal: Boolean = cur match {
+        case _ if escaped => escaped = false ; false
+        case '\\'         => escaped = true ; false
+        case `q` | EOF    => true
+        case _            => false
+      }
+      while (!terminal) bump()
+      !done
+    }
+    // Skip to a word boundary, where words can be quoted and quotes can be escaped
+    def skipToDelim(): Boolean = {
       var escaped = false
-      var Q = EOF
-      var lastQ = 0
-      def inQuote = Q != EOF
-      def badquote() = errorFn(s"Unmatched quote [${lastQ}](${line.charAt(lastQ)})")
-      def finish(): Boolean = if (!inQuote) !escaped else { badquote(); false}
+      def quote() = { qpos += pos ; bump() }
       @tailrec def advance(): Boolean = cur match {
-        case EOF                              => finish()
-        case _ if escaped                     => escaped = false; put(); advance()
-        case '\\'                             => escaped = true; bump(); advance()
-        case q if q == Q                      => Q = EOF; bump(); advance()
-        case q @ (DQ | SQ) if !inQuote        => Q = q; lastQ = pos; bump(); advance()
-        case c if isWhitespace(c) && !inQuote => finish()
-        case _                                => put(); advance()
+        case _ if escaped         => escaped = false ; bump() ; advance()
+        case '\\'                 => escaped = true ; bump() ; advance()
+        case q @ (DQ | SQ)        => { quote() ; skipToQuote(q) } && { quote() ; advance() }
+        case EOF                  => true
+        case c if isWhitespace(c) => true
+        case _                    => bump(); advance()
       }
       advance()
     }
+    def skipWhitespace() = while (isWhitespace(cur)) bump()
+    def copyText() = {
+      val buf = new Builder
+      var p = start
+      var i = 0
+      while (p < pos) {
+        if (i >= qpos.size) {
+          buf.append(line, p, pos)
+          p = pos
+        } else if (p == qpos(i)) {
+          buf.append(line, qpos(i)+1, qpos(i+1))
+          p = qpos(i+1)+1
+          i += 2
+        } else {
+          buf.append(line, p, qpos(i))
+          p = qpos(i)
+        }
+      }
+      buf.toString
+    }
     def text() = {
-      val res = buf.toString
-      buf.setLength(0)
+      val res =
+        if (qpos.isEmpty) line.substring(start, pos)
+        else if (qpos(0) == start && qpos(1) == pos) line.substring(start+1, pos-1)
+        else copyText()
+      qpos.clear()
       res
     }
+    def badquote() = errorFn(s"Unmatched quote [${qpos.last}](${line.charAt(qpos.last)})")
+
     @tailrec def loop(): List[String] = {
       skipWhitespace()
-      if (done) accum.toList
-      else if (!word()) Nil
+      start = pos
+      if (done) accum.reverse
+      else if (!skipToDelim()) { badquote() ; Nil }
       else {
-        accum += text()
+        accum ::= text()
         loop()
       }
     }
diff --git a/test/junit/scala/sys/process/ParserTest.scala b/test/junit/scala/sys/process/ParserTest.scala
index 0417d42c50d7..5673d9068878 100644
--- a/test/junit/scala/sys/process/ParserTest.scala
+++ b/test/junit/scala/sys/process/ParserTest.scala
@@ -51,17 +51,9 @@ class ParserTest {
   @Test def `leading quote is escaped`: Unit = {
     check("echo", "hello, world!")("""echo "hello, world!" """)
     check("echo", "hello, world!")("""echo hello,' 'world! """)
-    check("echo", """"hello,""", """world!"""")("""echo \"hello, world!\" """)
-    check("""a"b"c""")("""a\"b\"c""")
-    check("a", "'b", "'", "c")("""a \'b \' c""")
-    check("a", """\b """, "c")("""a \\'b ' c""")
-  }
-  /* backslash is stripped in normal shell usage.
-  ➜  ~ ls \"hello world\"
-  ls: cannot access '"hello': No such file or directory
-  ls: cannot access 'world"': No such file or directory
-  */
-  @Test def `escaped quotes lose backslash`: Unit = {
-    check("ls", "\"hello", "world\"")("""ls \"hello world\"""")
+    check("echo", """\"hello,""", """world!\"""")("""echo \"hello, world!\" """)
+    check("""a\"b\"c""")("""a\"b\"c""")
+    check("a", "\\'b", "\\'", "c")("""a \'b \' c""")
+    check("a", "\\\\b ", "c")("""a \\'b ' c""")
   }
 }