diff --git a/nbresnote.py b/nbresnote.py
index 92b8b34cf8259fe635b290cefde82217acfd3051..229fc6aa3dee8842763fa9ad6af1bd4e5f899045 100644
--- a/nbresnote.py
+++ b/nbresnote.py
@@ -1,6 +1,6 @@
 import json, base64, os, pickle, datetime, string, re
 
-__version__ = "0.1.10"
+__version__ = "0.1.11"
 ### from ipynb extract markdown and noted output for document organization
 
 class nbparser:
@@ -63,7 +63,11 @@ class nbparser:
         for i, cell in enumerate(notebook['cells']):
             if not cell["source"]:continue
             if cell["cell_type"] == 'markdown': #markdown 
+                if not (("source" in cell) and (len(cell["source"])!=0) and cell["source"][0].lstrip()):
+                    # skip error/empty markdown cell.
+                    continue
                 a = cell["source"][0].lstrip()
+                
                 #header parsing
                 if  a[0]== "#":
                     header = a.split()[0]
@@ -290,6 +294,10 @@ def write_daily(note_path, mod, record):
 
 
 shellsource = f"""#!/bin/bash
+##### nbresnote #####
+# {__version__}
+set -e
+
 source ~/.bashrc
 
 {"conda activate "+os.environ["CONDA_DEFAULT_ENV"] if "CONDA_DEFAULT_ENV" in os.environ else ""}
@@ -309,13 +317,56 @@ echo "nothing to commit"
 else
 git commit -m "Auto commit from nbresnote `date +%F`"
 fi
+##### nbresnote #####
 """
 
-pushsource = """#!/bin/bash
+pushsource = f"""#!/bin/bash
+##### nbresnote #####
+# {__version__}
+set -e
+
 cd wiki
 git fetch && git pull && git push
+##### nbresnote #####
 """
 
+def install():
+    """install action for git repository
+
+    Parameters
+    ----------
+    append : bool, optional
+        if `True`, the hook will be written in tail of each hooks. By default, `False`.
+
+    Raises
+    ------
+    OSError
+        _description_
+    """
+    #Installation
+    # Setting git/hooks pre-commit and pre-push
+    if not os.path.exists(".git"):
+        raise OSError("Please run on the base folder of git repository.")
+    #if not os.path.exists(".git/hooks/pre-commit"):
+    print("Creating 'pre-commit' file on '.git/hooks/'.")
+    with open(".git/hooks/pre-commit","w") as f:
+        f.write(shellsource)
+    print("Change mod of 'pre-commit' file on '.git/hooks/' into 755(rwxr-xr-x).")
+    os.chmod(".git/hooks/pre-commit", 0o755)
+    #else:
+        #print("Warning : Already exists 'pre-commit' file on '.git/hooks/'. Command ignored.")
+    #if not os.path.exists(".git/hooks/pre-push"):
+    print("Creating 'pre-push' file on '.git/hooks/'.")
+    with open(".git/hooks/pre-push","w") as f:
+        f.write(pushsource)
+    print("Change mod of 'pre-push' file on '.git/hooks/' into 755(rwxr-xr-x).")
+    os.chmod(".git/hooks/pre-push", 0o755)
+    #else:
+        #print("Warning : Already exists 'pre-push' file on '.git/hooks/'. Command ignored.")
+    print("Done.")
+    return 0 #success 0 fail 1
+    
+    
 
 if __name__ =="__main__":
     import sys
@@ -331,30 +382,7 @@ if __name__ =="__main__":
             targets = open("__tmp__files").readlines()
             #print(targets) #DEBUG
         elif sys.argv[1] == "install":
-            #Installation
-            # Setting git/hooks pre-commit and pre-push
-            if not os.path.exists(".git"):
-                raise OSError("Please run on the base folder of git repository.")
-            if not os.path.exists(".git/hooks/pre-commit"):
-                print("Creating 'pre-commit' file on '.git/hooks/'.")
-                with open(".git/hooks/pre-commit","a") as f:
-                    f.write(shellsource)
-                print("Change mod of 'pre-commit' file on '.git/hooks/' into 755(rwxr-xr-x).")
-                os.chmod(".git/hooks/pre-commit", 0o755)
-            else:
-                print("Warning : Already exists 'pre-commit' file on '.git/hooks/'. Command ignored.")
-            if not os.path.exists(".git/hooks/pre-push"):
-                print("Creating 'pre-push' file on '.git/hooks/'.")
-                with open(".git/hooks/pre-push","a") as f:
-                    f.write(pushsource)
-                print("Change mod of 'pre-push' file on '.git/hooks/' into 755(rwxr-xr-x).")
-                os.chmod(".git/hooks/pre-push", 0o755)
-            else:
-                print("Warning : Already exists 'pre-push' file on '.git/hooks/'. Command ignored.")
-            print("Done.")
-            
-            exit(0)
-
+            exit(install())
         else:
             targets = sys.argv[1:]