diff --git a/modules/utils.py b/modules/utils.py
new file mode 100644
index 0000000..9e6f29a
--- /dev/null
+++ b/modules/utils.py
@@ -0,0 +1,29 @@
+from subprocess import CalledProcessError
+from subprocess import check_output
+from subprocess import STDOUT
+
+
+class CommandPrinter(object):
+    """Command consumer that just prints the commands that it receives."""
+
+    def consume(self, command, directory):
+        print("{}$ {}".format(directory, ' '.join(command)))
+
+
+class CommandRunner(object):
+    """Command consumer that runs the commands that it receives."""
+
+    def consume(self, command, directory):
+        """
+        Run the given command in the given directory and print the stdout and
+        stderr. If an exception is thrown while running the command, it will be
+        rethrown as a RuntimeError.
+        """
+        # FIXME: This prints the results after the command has finished running.
+        # For long-running commands (e.g. an LLVM build) we'll want live
+        # output.
+        try:
+            print(str(check_output(command, stderr=STDOUT, cwd=directory), 'utf-8'))
+        except CalledProcessError as exc:
+            raise RuntimeError(
+                "Error while running command\n{}".format(str(exc.output, 'utf-8'))) from exc