src/Pure/System/isabelle_system.scala

 import scala.jdk.CollectionConverters._
 
 
 object Isabelle_System
 {
-  /* settings */
+  /* settings environment */
 
   def settings(putenv: List[(String, String)] = Nil): JMap[String, String] =
   {
     val env0 = isabelle.setup.Environment.settings()
     if (putenv.isEmpty) env0

         val hg = Mercurial.repository(root)
         hg.tags(rev = hg.parent())
       }
       else ""
     }
+
+  def export_isabelle_identifier(isabelle_identifier: String): String =
+    if (isabelle_identifier == "") ""
+    else "export ISABELLE_IDENTIFIER=" + Bash.string(isabelle_identifier) + "\n"
 
   def isabelle_identifier(): Option[String] = proper_string(getenv("ISABELLE_IDENTIFIER"))
 
   def isabelle_heading(): String =
     isabelle_identifier() match {

       description = description, cwd = cwd, env = env, redirect = redirect, cleanup = cleanup).
       result(input = input, progress_stdout = progress_stdout, progress_stderr = progress_stderr,
         watchdog = watchdog, strict = strict)
   }
 
+
+  /* command-line tools */
+
+  def require_command(cmd: String, test: String = "--version"): Unit =
+  {
+    if (!bash(Bash.string(cmd) + " " + test).ok) error("Missing system command: " + quote(cmd))
+  }
+
   private lazy val gnutar_check: Boolean =
     try { bash("tar --version").check.out.containsSlice("GNU tar") || error("") }
     catch { case ERROR(_) => false }
 
   def gnutar(

       (if (original_owner) "" else "--owner=root --group=staff ") +
       (if (strip <= 0) "" else "--strip-components=" + strip + " ")
 
     if (gnutar_check) bash("tar " + options + args, redirect = redirect)
     else error("Expected to find GNU tar executable")
-  }
-
-  def require_command(cmd: String, test: String = "--version"): Unit =
-  {
-    if (!bash(Bash.string(cmd) + " " + test).ok) error("Missing system command: " + quote(cmd))
   }
 
   def hostname(): String = bash("hostname -s").check.out
 
   def open(arg: String): Unit =

       else open(name)
     }
     external
   }
 
-  def export_isabelle_identifier(isabelle_identifier: String): String =
-    if (isabelle_identifier == "") ""
-    else "export ISABELLE_IDENTIFIER=" + Bash.string(isabelle_identifier) + "\n"
 
 
   /** Isabelle resources **/
 
   /* repository clone with Admin */