diff --git a/ChangeLog b/ChangeLog
index da3df62d56..6077fb52c7 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Thu Aug 16 00:36:52 2007  Tanaka Akira  <akr@fsij.org>
+
+	* lib/tmpdir.rb (Dir.mktmpdir): new method.  [ruby-dev:31416]
+
 Wed Aug 15 18:57:30 2007  Koichi Sasada  <ko1@atdot.net>
 
 	* gc.c (os_live_obj): fix to skip T_VALUES.
diff --git a/lib/tmpdir.rb b/lib/tmpdir.rb
index 434d1bf053..ada9ed5544 100644
--- a/lib/tmpdir.rb
+++ b/lib/tmpdir.rb
@@ -4,6 +4,8 @@
 # $Id$
 #
 
+require 'fileutils'
+
 class Dir
 
   @@systmpdir = '/tmp'
@@ -42,4 +44,63 @@ class Dir
     end
     File.expand_path(tmp)
   end
+
+  # Dir.mktmpdir creates a temporary directory.
+  #
+  # The directory is created with 0700 permission.
+  # The name of the directory is prefixed
+  # with <i>prefix</i> argument.
+  # If <i>prefix</i> is not given,
+  # the prefix "d" is used.
+  #
+  # The directory is created under Dir.tmpdir or
+  # the optional second argument <i>tmpdir</i> if given.
+  #
+  # If a block is given,
+  # it is yielded with the path of the directory.
+  # The directory is removed before Dir.mktmpdir returns.
+  # The value of the block is returned.
+  #
+  #  Dir.mktmpdir {|dir|
+  #    # use the directory...
+  #    open("#{dir}/foo", "w") { ... }
+  #  }
+  #
+  # If a block is not given,
+  # The path of the directory is returned.
+  # In this case, Dir.mktmpdir doesn't remove the directory.
+  #
+  #  dir = Dir.mktmpdir
+  #  begin
+  #    # use the directory...
+  #    open("#{dir}/foo", "w") { ... }
+  #  ensure
+  #    # remove the directory.
+  #    FileUtils.remove_entry_secure dir
+  #  end
+  #
+  def Dir.mktmpdir(prefix="d", tmpdir=nil)
+    tmpdir ||= Dir.tmpdir
+    t = Time.now.strftime("%Y%m%d")
+    n = nil
+    begin
+      path = "#{tmpdir}/#{prefix}#{t}-#{$$}-#{rand(0x100000000).to_s(36)}"
+      path << "-#{n}" if n
+      Dir.mkdir(path, 0700)
+    rescue Errno::EEXIST
+      n ||= 0
+      n += 1
+      retry
+    end
+
+    if block_given?
+      begin
+        yield path
+      ensure
+        FileUtils.remove_entry_secure path
+      end
+    else
+      path
+    end
+  end
 end