diff --git a/tools/navigation.py b/tools/navigation.py
index 6985bff..a7044f0 100755
--- a/tools/navigation.py
+++ b/tools/navigation.py
@@ -1,6 +1,8 @@
 #!/usr/bin/env python3
-import os
 import glob
+import os
+import re
+import sys
 import yaml
 
 
@@ -29,14 +31,31 @@ def traverse_siblings(pages, start, sibling='next'):
     page = pages[page]['siblings'].get(sibling)
 
 
-def create_intro_toc(pages, start, offset=2):
+def create_intro_toc(pages, start, offset=2, file=sys.stdout):
   for num, page in enumerate(traverse_siblings(pages, start)):
     data = pages[page]
     title = most_appropriate_title(data)
-    print(f"{num + offset}. [{title}]({page})\n")
+    print(f"{num + offset}. [{title}]({page})\n", file=file)
 
 
-def create_navbar(pages, start):
+def overwrite_info_toc(pages, start, offset=2):
+  old_name = "gdb/index.md"
+  new_name = "gdb/.index.new"
+  with open(old_name) as orig:
+    with open(new_name, 'w') as new:
+      found = False
+      for line in orig:
+        if found and '</div' in line:
+          found = False
+          create_intro_toc(pages, start, offset=offset, file=new)
+        if not found and f'{offset}. [' in line:
+          found = True
+        if not found:
+          new.write(line)
+  os.rename(new_name, old_name)
+
+
+def create_navbar(pages, start, file=sys.stdout):
   longest_link = max(map(len, traverse_siblings(pages, start))) + 2
 
   for page in traverse_siblings(pages, start):
@@ -44,11 +63,28 @@ def create_navbar(pages, start):
     title = most_appropriate_title(data)
     linksq = f"'{page}'"
     linkdq = f'"{page}"'
-    print(f'    <a href={linkdq:{longest_link}s} class="{{{{#is meta.url {linksq:{longest_link}s}}}}}active {{{{/is}}}}dropdown-item">{title}</a>')
+    print(f'    <a href={linkdq:{longest_link}s} class="{{{{#is meta.url {linksq:{longest_link}s}}}}}active {{{{/is}}}}dropdown-item">{title}</a>', file=file)
 
 
-def check_nav_consistency(pages, first):
-  for page in traverse_siblings(pages, first):
+def overwrite_navbar(pages, start):
+  old_name = "_gdb-menu.hbs"
+  new_name = ".gdb-menu.new"
+  with open(old_name) as orig:
+    with open(new_name, 'w') as new:
+      found = False
+      for line in orig:
+        if found and '</div' in line:
+          found = False
+          create_navbar(pages, start, file=new)
+        if not found:
+          new.write(line)
+        if '="/gdb/"' in line:
+          found = True
+  os.rename(new_name, old_name)
+
+
+def check_nav_consistency(pages):
+  for page in pages:
     siblings = pages[page]['siblings']
     for sibling in 'prev', 'next':
       sibling_data = pages.get(siblings.get(sibling))
@@ -59,14 +95,48 @@ def check_nav_consistency(pages, first):
           print(f"{page}: caption mismatch for {sibling}: expected {sibling_title!r}, got {link_title!r}")
 
 
+def overwrite_nav_meta(pages):
+  for page in pages:
+    siblings = pages[page]['siblings']
+    old_name = page.lstrip("/") + '.md'
+    new_name = ".new.md"
+    with open(old_name) as orig:
+      with open(new_name, "w") as new:
+        for line in orig:
+          match = None
+          for sibling in 'prev', 'next':
+            sibling_data = pages.get(siblings.get(sibling))
+            if sibling_data:
+              sibling_title = most_appropriate_title(sibling_data)
+              match = re.match(f"( *{sibling}Caption: *).*", line)
+              if match:
+                new.write(match.group(1) + sibling_title + "\n")
+                break
+          if not match:
+            new.write(line)
+
+    os.rename(new_name, old_name)
+
+
+def check_excluded_pages(pages, first):
+  missing = set(pages.keys()) - set(traverse_siblings(pages, first))
+  if missing:
+    print(f"Unlinked pages (starting from {first}): {missing}")
+
+
 def main():
   os.chdir("../public")
   pages = {fix_web_path(file): parse_page_data(file) for file in get_all_pages()}
   *_, first = traverse_siblings(pages, next(iter(pages)), sibling="prev")
-  create_intro_toc(pages, first)
-  create_navbar(pages, first)
-  check_nav_consistency(pages, first)
-  return 0
+  check_excluded_pages(pages, first)
+  if '--write' in sys.argv:
+    overwrite_info_toc(pages, first)
+    overwrite_navbar(pages, first)
+    overwrite_nav_meta(pages)
+  else:
+    create_intro_toc(pages, first)
+    create_navbar(pages, first)
+    check_nav_consistency(pages)
 
 
 if __name__ == '__main__':