--- a/dmri.py	Fri Nov 03 13:30:34 2017 -0400
+++ b/dmri.py	Fri Nov 03 13:33:58 2017 -0400
@@ -25,16 +25,16 @@
             shutil.move(source_entry, destination_directory)
     if remove_source_dir:
         os.rmdir(source_directory)
-
-input_dir = 'input_dir'
-# Get input data.
-fetch_sherbrooke_3shell()
-# MNove inputs to working directory.
 source_dir = os.path.abspath(os.path.join('home', 'greg', '.dipy', 'sherbrooke_3shell'))
-move_directory_files(source_dir, input_dir)
-fdwi = os.path.join(input_dir, 'HARDI193.nii.gz')
-fbval = os.path.join(input_dir, 'HARDI193.bval')
-fbvec = os.path.join(input_dir, 'HARDI193.bvec')
+dest_dir = 'input_dir'
+if not os.path.exists(source_dir):
+    # Get input data.
+    fetch_sherbrooke_3shell()
+# Move inputs to working directory.
+move_directory_files(source_dir, dest_dir, copy=True)
+fdwi = os.path.join(dest_dir, 'HARDI193.nii.gz')
+fbval = os.path.join(dest_dir, 'HARDI193.bval')
+fbvec = os.path.join(dest_dir, 'HARDI193.bvec')
 # Load the dMRI datasets.
 img = nibabel.load(fdwi)
 data = img.get_data()