ENH/TMP: Preliminary support for bash scripts.

 - Changing the Question model to add a language attribute.
 - Moving python_server.py -> code_server.py.
 - Adding functionality to test for Shell scripts.  This is still
   incomplete since the shell code checker seems to have some problems.
 - Modified the xmlrpc_clients to support multiple languages and right
   now two.
 - Using setgid/setuid instead of setegid/seteuid in the code_server.py..
 - Adding a bash example to the sample_questions.py.

The shell script support doesn't quite work yet but this is really a
code_server/checking issue.

4 files changed, 45 insertions, 9 deletions

diff --git a/exam/management/commands/load_questions_xml.py b/exam/management/commands/load_questions_xml.py
index aa403dd..b4151ae 100644
--- a/exam/management/commands/load_questions_xml.py
+++ b/exam/management/commands/load_questions_xml.py
@@ -35,6 +35,9 @@ def load_questions_xml(filename):
         desc_node = question.getElementsByTagName("description")[0]
         description = (desc_node.childNodes[0].data).strip()
 
+        lang_node = question.getElementsByTagName("language")[0]
+        language = (lang_node.childNodes[0].data).strip()
+
         points_node = question.getElementsByTagName("points")[0]
         points = int((points_node.childNodes[0].data).strip()) \
                  if points_node else 1
@@ -45,6 +48,7 @@ def load_questions_xml(filename):
         new_question = Question(summary=summary,
                                 description=description,
                                 points=points,
+                                language=language,
                                 test=test)
         new_question.save()
     
diff --git a/exam/models.py b/exam/models.py
index d433c7c..ef4312f 100644
--- a/exam/models.py
+++ b/exam/models.py
@@ -12,6 +12,11 @@ class Profile(models.Model):
     position = models.CharField(max_length=64)
 
 
+LANGUAGE_CHOICES = (
+        ("python", "Python"),
+        ("bash", "Bash"),
+        )
+
 ################################################################################
 class Question(models.Model):
     """A question in the database."""
@@ -29,6 +34,9 @@ class Question(models.Model):
     # This is simple Python code.
     test = models.TextField()
 
+    # The language being tested.
+    language = models.CharField(max_length=10, choices=LANGUAGE_CHOICES)
+
     # Is this question active or not.  If it is inactive it will not be used
     # when creating a QuestionPaper.
     active = models.BooleanField(default=True)
diff --git a/exam/views.py b/exam/views.py
index bafd0be..1f92553 100644
--- a/exam/views.py
+++ b/exam/views.py
@@ -13,7 +13,7 @@ from django.http import Http404
 # Local imports.
 from exam.models import Quiz, Question, QuestionPaper, Profile, Answer, User
 from exam.forms import UserRegisterForm, UserLoginForm
-from exam.xmlrpc_clients import python_server
+from exam.xmlrpc_clients import code_server
 from settings import URL_ROOT
 
 # The directory where user data can be saved.
@@ -203,7 +203,8 @@ def check(request, q_id):
     # with the code executed safely in a separate process (the python_server.py)
     # running as nobody.
     user_dir = get_user_dir(user)
-    success, err_msg = python_server.run_code(answer, question.test, user_dir)
+    success, err_msg = code_server.run_code(answer, question.test, 
+                                            user_dir, question.language)
     new_answer.error = err_msg
 
     if success:
diff --git a/exam/xmlrpc_clients.py b/exam/xmlrpc_clients.py
index 115ee6e..01172d7 100644
--- a/exam/xmlrpc_clients.py
+++ b/exam/xmlrpc_clients.py
@@ -4,7 +4,7 @@ import random
 import socket
 
 
-class PythonServer(object):
+class CodeServer(object):
     """A class that manages accesing the farm of Python servers and making
     calls to them such that no one XMLRPC server is overloaded.
     """
@@ -12,19 +12,41 @@ class PythonServer(object):
         servers = [ServerProxy('http://localhost:%d'%(x)) for x in SERVER_PORTS]
         self.servers = servers
         self.indices = range(len(SERVER_PORTS))
+        self.methods = {"python": 'run_python_code',
+                        "bash": 'run_bash_code'}
     
-    def run_code(self, answer, test_code, user_dir):
-        """See the documentation of the method of the same name in 
-        python_server.py.
+    def run_code(self, answer, test_code, user_dir, language):
+        """Tests given code (`answer`) with the `test_code` supplied.  If the
+        optional `in_dir` keyword argument is supplied it changes the directory
+        to that directory (it does not change it back to the original when
+        done).  The parameter language specifies which language to use for the
+        tests.
+
+        Parameters
+        ----------
+        answer : str
+            The user's answer for the question.
+        test_code : str
+            The test code to check the user code with.
+        user_dir : str (directory)
+            The directory to run the tests inside.
+        language : str
+            The programming language to use.
+
+        Returns
+        -------
+        A tuple: (success, error message).
         """
+        method_name = self.methods[language]
         done = False
-        result = [False, 'Unable to connect to any Python servers!']
+        result = [False, 'Unable to connect to any code servers!']
         # Try to connect a few times if not, quit.
         count = 5
         while (not done) and (count > 0):
             try:
                 server = self._get_server()
-                result = server.run_code(answer, test_code, user_dir)
+                method = getattr(server, method_name)
+                result = method(answer, test_code, user_dir)
             except socket.error:
                 count -= 1
             else:
@@ -38,4 +60,5 @@ class PythonServer(object):
 
 # views.py calls this Python server which forwards the request to one
 # of the running servers.
-python_server = PythonServer()
+code_server = CodeServer()
+