tuned signature -- more like ML version;

--- a/src/Pure/System/isabelle_system.scala	Sat Feb 13 21:10:13 2016 +0100
+++ b/src/Pure/System/isabelle_system.scala	Sat Feb 13 21:17:08 2016 +0100
@@ -167,7 +167,7 @@
 
   def mkdirs(path: Path): Unit =
     if (!path.is_dir) {
-      bash("perl -e \"use File::Path make_path; make_path(" + File.shell_path(path) + ");\"")
+      bash_result("perl -e \"use File::Path make_path; make_path(" + File.shell_path(path) + ");\"")
       if (!path.is_dir) error("Failed to create directory: " + quote(File.platform_path(path)))
     }
 
@@ -316,7 +316,7 @@
     }
   }
 
-  def bash_env(cwd: JFile, env: Map[String, String], script: String,
+  def bash_result(script: String, cwd: JFile = null, env: Map[String, String] = null,
     progress_stdout: String => Unit = (_: String) => (),
     progress_stderr: String => Unit = (_: String) => (),
     progress_limit: Option[Long] = None,
@@ -342,7 +342,13 @@
     }
   }
 
-  def bash(script: String): Bash.Result = bash_env(null, null, script)
+  def bash(script: String): Int =
+  {
+    val result = bash_result(script)
+    Output.warning(Library.trim_line(result.err))
+    Output.writeln(Library.trim_line(result.out))
+    result.rc
+  }
 
 
   /* system tools */
@@ -365,13 +371,13 @@
   }
 
   def open(arg: String): Unit =
-    bash("exec \"$ISABELLE_OPEN\" '" + arg + "' >/dev/null 2>/dev/null &")
+    bash_result("exec \"$ISABELLE_OPEN\" '" + arg + "' >/dev/null 2>/dev/null &")
 
   def pdf_viewer(arg: Path): Unit =
-    bash("exec \"$PDF_VIEWER\" '" + File.standard_path(arg) + "' >/dev/null 2>/dev/null &")
+    bash_result("exec \"$PDF_VIEWER\" '" + File.standard_path(arg) + "' >/dev/null 2>/dev/null &")
 
   def hg(cmd_line: String, cwd: Path = Path.current): Bash.Result =
-    bash("cd " + File.shell_path(cwd) + " && \"${HG:-hg}\" " + cmd_line)
+    bash_result("cd " + File.shell_path(cwd) + " && \"${HG:-hg}\" " + cmd_line)
 
 
   /** Isabelle resources **/

--- a/src/Pure/Tools/build.scala	Sat Feb 13 21:10:13 2016 +0100
+++ b/src/Pure/Tools/build.scala	Sat Feb 13 21:17:08 2016 +0100
@@ -602,7 +602,7 @@
 
     private val result =
       Future.thread("build") {
-        Isabelle_System.bash_env(info.dir.file, env, script,
+        Isabelle_System.bash_result(script, info.dir.file, env,
           progress_stdout = (line: String) =>
             Library.try_unprefix("\floading_theory = ", line) match {
               case Some(theory) => progress.theory(name, theory)

--- a/src/Tools/jEdit/src/active.scala	Sat Feb 13 21:10:13 2016 +0100
+++ b/src/Tools/jEdit/src/active.scala	Sat Feb 13 21:17:08 2016 +0100
@@ -33,9 +33,8 @@
                 Standard_Thread.fork("browser") {
                   val graph_file = Isabelle_System.tmp_file("graph")
                   File.write(graph_file, XML.content(body))
-                  Isabelle_System.bash_env(null,
-                    Map("GRAPH_FILE" -> File.standard_path(graph_file)),
-                    "\"$ISABELLE_TOOL\" browser -c \"$GRAPH_FILE\" &")
+                  Isabelle_System.bash_result("\"$ISABELLE_TOOL\" browser -c \"$GRAPH_FILE\" &",
+                    env = Map("GRAPH_FILE" -> File.standard_path(graph_file)))
                 }
 
               case XML.Elem(Markup(Markup.GRAPHVIEW, _), body) =>