src/Pure/System/bash.scala

   def strings(ss: Iterable[String]): String =
     ss.iterator.map(Bash.string).mkString(" ")
 
 
   /* process and result */
+
+  def context(script: String,
+    user_home: String = "",
+    isabelle_identifier: String = "",
+    cwd: Path = Path.current
+  ): String = {
+    if_proper(user_home,
+      "export USER_HOME=" + Bash.string(user_home) + "\n") +
+    if_proper(isabelle_identifier,
+      "export ISABELLE_IDENTIFIER=" + Bash.string(isabelle_identifier) + "\n") +
+    (if (cwd == null || cwd.is_current) "" else "cd " + quote(cwd.implode) + "\n") +
+    script
+  }
 
   private def make_description(description: String): String =
     proper_string(description) getOrElse "bash_process"
 
   def local_bash_process(): String =