diff --git a/data/core/commands/dialog.lua b/data/core/commands/dialog.lua
index f6df69aa..90606abb 100644
--- a/data/core/commands/dialog.lua
+++ b/data/core/commands/dialog.lua
@@ -1,5 +1,6 @@
 local core = require "core"
 local command = require "core.command"
+local common = require "core.common"
 
 command.add("core.nagview", {
   ["dialog:previous-entry"] = function()
@@ -15,13 +16,13 @@ command.add("core.nagview", {
   ["dialog:select-yes"] = function()
     local v = core.active_view
     if v ~= core.nag_view then return end
-    v:change_hovered(findindex(v.options, "default_yes"))
+    v:change_hovered(common.find_index(v.options, "default_yes"))
     command.perform "dialog:select"
   end,
   ["dialog:select-no"] = function()
     local v = core.active_view
     if v ~= core.nag_view then return end
-    v:change_hovered(findindex(v.options, "default_no"))
+    v:change_hovered(common.find_index(v.options, "default_no"))
     command.perform "dialog:select"
   end,
   ["dialog:select"] = function()
diff --git a/data/core/commands/files.lua b/data/core/commands/files.lua
index a366d43e..b2fdb336 100644
--- a/data/core/commands/files.lua
+++ b/data/core/commands/files.lua
@@ -1,37 +1,11 @@
 local core = require "core"
 local command = require "core.command"
-
-local function mkdirp(path)
-  local segments = {}
-  local pos = 1
-  while true do
-    local s, e = string.find(path, "[/\\]+", pos)
-    if not s then break end
-    table.insert(segments, string.sub(str, pos, s - 1))
-    pos = e + 1
-  end
-  table.insert(segments, string.sub(str, pos))
-  if segments[#segments] == '' then
-    table.remove(segments)
-  end
-
-  for i = 1, #segments do
-    local p = table.concat(segments, PATHSEP, 1, i)
-    local stat = system.get_file_info(p)
-    if stat and stat.type == "file" then
-      return nil, "path exists", p
-    end
-    local success, err = system.mkdir(p)
-    if not success then
-      return nil, err, p
-    end
-  end
-end
+local common = require "core.common"
 
 command.add(nil, {
   ["files:create-directory"] = function()
     core.command_view:enter("New directory name", function(text)
-      local success, err, path = mkdirp(text)
+      local success, err, path = common.mkdirp(text)
       if not success then
         core.error("cannot create directory %q: %s", path, err)
       end
diff --git a/data/core/common.lua b/data/core/common.lua
index 06ef2880..a2bbb06a 100644
--- a/data/core/common.lua
+++ b/data/core/common.lua
@@ -22,6 +22,13 @@ function common.round(n)
 end
 
 
+function common.find_index(tbl, prop)
+  for i, o in ipairs(tbl) do
+    if o[prop] then return i end
+  end
+end
+
+
 function common.lerp(a, b, t)
   if type(a) ~= "table" then
     return a + (b - a) * t
@@ -291,4 +298,26 @@ function common.relative_path(ref_dir, dir)
 end
 
 
+function common.mkdirp(path)
+  local stat = system.get_file_info(path)
+  if stat and stat.type then
+    return false, "path exists", path
+  end
+  local subdirs = {}
+  while path and path ~= "" do
+    local success_mkdir = system.mkdir(path)
+    if success_mkdir then break end
+    local updir, basedir = path:match("(.*)[/\\](.+)$")
+    table.insert(subdirs, 1, basedir or path)
+    path = updir
+  end
+  for _, dirname in ipairs(subdirs) do
+    path = path and path .. PATHSEP .. dirname or dirname
+    if not system.mkdir(path) then
+      return false, "cannot create directory", path
+    end
+  end
+  return true
+end
+
 return common
diff --git a/data/core/init.lua b/data/core/init.lua
index 5a70dbdb..24dccdd1 100644
--- a/data/core/init.lua
+++ b/data/core/init.lua
@@ -270,25 +270,12 @@ end
 -- create a directory using mkdir but may need to create the parent
 -- directories as well.
 local function create_user_directory()
-  local dirname_create = USERDIR
-  local basedir
-  local subdirs = {}
-  while dirname_create and dirname_create ~= "" do
-    local success_mkdir = system.mkdir(dirname_create)
-    if success_mkdir then break end
-    dirname_create, basedir = dirname_create:match("(.*)[/\\](.+)$")
-    if basedir then
-      subdirs[#subdirs + 1] = basedir
-    end
-  end
-  for _, dirname in ipairs(subdirs) do
-    dirname_create = dirname_create .. '/' .. dirname
-    if not system.mkdir(dirname_create) then
-      error("cannot create directory: \"" .. dirname_create .. "\"")
-    end
+  local success, err = common.mkdirp(USERDIR)
+  if not success then
+    error("cannot create directory \"" .. USERDIR .. "\": " .. err)
   end
   for _, modname in ipairs {'plugins', 'colors', 'fonts'} do
-    local subdirname = dirname_create .. '/' .. modname
+    local subdirname = USERDIR .. PATHSEP .. modname
     if not system.mkdir(subdirname) then
       error("cannot create directory: \"" .. subdirname .. "\"")
     end
diff --git a/data/core/nagview.lua b/data/core/nagview.lua
index 1f48d8d6..6d6f89f4 100644
--- a/data/core/nagview.lua
+++ b/data/core/nagview.lua
@@ -170,12 +170,6 @@ function NagView:draw()
   end
 end
 
-local function findindex(tbl, prop)
-  for i, o in ipairs(tbl) do
-    if o[prop] then return i end
-  end
-end
-
 function NagView:get_message_height()
   local h = 0
   for str in string.gmatch(self.message, "(.-)\n") do
@@ -196,7 +190,7 @@ function NagView:next()
     -- self.target_height is the nagview height needed to display the message and
     -- the buttons, excluding the top and bottom padding space.
     self.target_height = math.max(message_height, self:get_buttons_height())
-    self:change_hovered(findindex(self.options, "default_yes"))
+    self:change_hovered(common.find_index(self.options, "default_yes"))
   end
   self.force_focus = self.message ~= nil
   core.set_active_view(self.message ~= nil and self or core.last_active_view)