diff --git a/project/sync/cli.py b/project/sync/cli.py
index 253e1c6..7d3aee3 100644
--- a/project/sync/cli.py
+++ b/project/sync/cli.py
@@ -3,15 +3,21 @@ from project.utils import config, repos
 
 
 @click.command('sync')
-@click.option('--private/--no-private', default=False)
-def cli(private):
+@click.option('--private', default=False)
+@click.option('--clean', default=False)
+def cli(private, clean):
+    if clean:
+        print("Cleaning")
+        repos.clean()
     if not config.has_basics():
         print("You do not have all the basic requirements set.")
         return 1
-    exit_code = repos.clone_public_data()
-    if private and exit_code == 0:
+    error = repos.clone_public_data()
+    if error:
+        return 1
+    if private:
         if not config.get('private_repo'):
             print("private repo not set")
             return 1
-        exit_code = repos.clone_private_data()
-    return exit_code
+        error = repos.clone_private_data()
+    return int(error)
diff --git a/project/utils/repos.py b/project/utils/repos.py
index 1713275..2b8435a 100644
--- a/project/utils/repos.py
+++ b/project/utils/repos.py
@@ -1,20 +1,24 @@
-import os
+import os, shutil
 from distutils.dir_util import copy_tree
-from . import config, constants
+from . import config, constants, shell
 
 
 def clone_public_data():
     if os.path.isdir(constants.PUBLIC_DATA_DIR):
         initial = os.getcwd()
         go_to_data()
-        exit_code = os.system("git pull")
+        out, error = shell.call("git pull")
         os.chdir(initial)
-        return exit_code
+        if error:
+            print("Error:", out)
+        return error
 
-    exit_code = os.system("git clone -b master --single-branch {} {}"
-        .format(config.get('public_repo'),
-        constants.PUBLIC_DATA_DIR))
-    return exit_code
+    out, error = shell.call(
+        "git clone -b master --single-branch {} {}".format(
+        config.get('public_repo'),
+        constants.PUBLIC_DATA_DIR)
+    )
+    return error
 
 
 def clone_private_data():
@@ -22,19 +26,25 @@ def clone_private_data():
     if os.path.isdir(constants.PRIVATE_DATA_DIR):
         initial = os.getcwd()
         os.chdir(constants.PRIVATE_DATA_DIR)
-        exit_code = os.system("git pull")
+        out, error = shell.call("git pull")
         os.chdir(initial)
+        if error:
+            print("Error:", out)
+        return error
     else:
-        exit_code = os.system("git clone -b master --single-branch {} {}"
-            .format(config.get('private_repo'), constants.PRIVATE_DATA_DIR))
-    if exit_code != 0:
-        return exit_code
+        out, error = shell.call(
+        "git clone -b master --single-branch {} {}".format(
+            config.get('private_repo'),
+            constants.PRIVATE_DATA_DIR)
+        )
+    if error:
+        return error
 
     copy_tree(
         constants.PRIVATE_DATA_DIR,
         constants.PUBLIC_DATA_DIR
     )
-    return exit_code
+    return error
 
 
 def has_data(data):
@@ -47,3 +57,7 @@ def go_to_data(subdir=''):
     path = os.path.join(constants.PUBLIC_DATA_DIR, subdir)
     os.chdir(path)
     return path
+
+def clean():
+    shutil.rmtree(constants.PUBLIC_DATA_DIR)
+    shutil.rmtree(constants.PRIVATE_DATA_DIR)
diff --git a/project/utils/shell.py b/project/utils/shell.py
new file mode 100644
index 0000000..d6d68d6
--- /dev/null
+++ b/project/utils/shell.py
@@ -0,0 +1,6 @@
+import subprocess
+
+def call(command):
+    shell = subprocess.Popen(command, stdout=subprocess.PIPE, shell=True)
+    output, error = shell.communicate()
+    return str(output), error