# Ruby/DL problem **URL:** \ **Category:** Ruby\ **Created:** [July 2, 2010, 5:37pm UTC](https://www.ruby-forum.com/t/ruby-dl-problem/191015 "2010-07-02T17:37:21Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![Aston](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/85f322/32.png) [@Aston](https://www.ruby-forum.com/u/Aston)\ **Post date:** [July 2, 2010, 5:37pm UTC](https://www.ruby-forum.com/t/ruby-dl-problem/191015/1 "2010-07-02T17:37:21Z")
Hello, I have very little experience with dl. But I want to use it to call SetEnvironmentVariable() from Win32. I could use FFI but cannot, since this script will be supplied to a customer where it is difficult to install. SetEnvironmentVariable on MSDN [SetEnvironmentVariableA function (processenv.h) - Win32 apps | Microsoft Learn](http://msdn.microsoft.com/en-us/library/ms686206(v=VS.85).aspx) reading sparse, old, and cryptic documentation I came up with this snippet, which of course does not work require ‘dl/import’ module Win32 extend DL::Importer extern “int SetEnvironmentVariableA( char\* lpName, char\* lpValue)” extern “int GetEnvironmentVariableA( char\* lpName, char\* lpValue, int size)” end buff = Array.new( 256, 0).pack(“c\*”) Win32.GetEnvironmentVariableA( “ENV\_VAR”, buff, 255) puts buff.unpack(“a\*”) this is the error i get D:/ruby/usr/lib/ruby/1.9.1/dl/import.rb:194:in `import_function': undefined method `sym’ for nil:NilClass (NoMethodError) from D:/ruby/usr/lib/ruby/1.9.1/dl/import.rb:118:in `extern' from test.rb:5:in `module:Win32’ from test.rb:3:in `’ machine is WinXP ruby 1.9.1 (2008-10-28 revision 19983) [i386-mswin32\_80] can anybody suggest a better signature ? Aston ---
**Author:** ![Aston](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/85f322/32.png) [@Aston](https://www.ruby-forum.com/u/Aston)\ **Post date:** [July 2, 2010, 7:16pm UTC](https://www.ruby-forum.com/t/ruby-dl-problem/191015/2 "2010-07-02T19:16:22Z")
On Fri, Jul 2, 2010 at 10:37 AM, Aston [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > which of course does not work > Win32.GetEnvironmentVariableA( “ENV\_VAR”, buff, 255) > ruby 1.9.1 (2008-10-28 revision 19983) [i386-mswin32\_80] > > can anybody suggest a better signature ? > > Aston I can’t help you with your issue, but I’m curious why it’s necessary. The MSDN page you link to says SetEnvironmentVariable is only for the current process. Doesn’t ENV do what you need? irb(main):001:0\> ENV[‘FOO’]=‘bar’ =\> “bar” irb(main):002:0\> `echo %FOO%` =\> “bar\n” irb(main):003:0\> ---
**Author:** ![Aston](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/85f322/32.png) [@Aston](https://www.ruby-forum.com/u/Aston)\ **Post date:** [July 3, 2010, 5:22pm UTC](https://www.ruby-forum.com/t/ruby-dl-problem/191015/3 "2010-07-03T17:22:07Z")
----- Original Message ---- > module Win32 > D:/ruby/usr/lib/ruby/1.9.1/dl/import.rb:194:in `import\_function’: undefined > Aston hmm, nobody here using Ruby.DL ? ---
**Author:** ![Aston](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/85f322/32.png) [@Aston](https://www.ruby-forum.com/u/Aston)\ **Post date:** [July 3, 2010, 5:50pm UTC](https://www.ruby-forum.com/t/ruby-dl-problem/191015/4 "2010-07-03T17:50:48Z")
On Jul 3, 12:20 pm, Aston [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > > this > > > this is the error i get > > > Aston > > hmm, nobody here using Ruby.DL ? Is not DL the problem, but the version you’re using. revision 19983 is _way_ older than latest released one: Pathlevel 378 was revision 26273 Lurking in the NEWS and ChangeLog pointed several changes in DL. Trying your example with latest RubyInstaller 1.9.1 release: C:\Users\Luis\Desktop\>ruby -v t.rb ruby 1.9.1p378 (2010-01-10 revision 26273) [i386-mingw32] C:/Users/Luis/Tools/Ruby/ruby-1.9.1-p378-i386-mingw32/lib/ruby/1.9.1/ dl/import.rb:116: warning: instance variable @type\_alias not initialized C:/Users/Luis/Tools/Ruby/ruby-1.9.1-p378-i386-mingw32/lib/ruby/1.9.1/ dl/import.rb:194: warning: instance variable @handler not initialized C:/Users/Luis/Tools/Ruby/ruby-1.9.1-p378-i386-mingw32/lib/ruby/1.9.1/ dl/import.rb:194:in `import_function': undefined method `sym’ for nil:NilClass (NoMethodError) from C:/Users/Luis/Tools/Ruby/ruby-1.9.1-p378-i386-mingw32/lib/ ruby/1.9.1/dl/import.rb:118:in `extern' from t.rb:5:in `module:Win32’ from t.rb:3:in `’ Which brings the question, why bother on doing this way when Ruby does it out of the box? ---
**Author:** ![Aston](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/85f322/32.png) [@Aston](https://www.ruby-forum.com/u/Aston)\ **Post date:** [July 4, 2010, 3:03am UTC](https://www.ruby-forum.com/t/ruby-dl-problem/191015/5 "2010-07-04T03:03:16Z")
Hi, At Sat, 3 Jul 2010 00:37:00 +0900, Aston wrote in [ruby-core:30996]: > module Win32 > extend DL::Importer > dlload “kernel32” # is this correct DLL? > extern “int SetEnvironmentVariableA( char\* lpName, char\* lpValue)” > extern “int GetEnvironmentVariableA( char\* lpName, char\* lpValue, int size)” > end The following patch refines the error messages. diff --git a/ext/dl/lib/dl/import.rb b/ext/dl/lib/dl/import.rb index fd23bc9…f9e8faf 100644 — a/ext/dl/lib/dl/import.rb +++ b/ext/dl/lib/dl/import.rb @@ -194,8 +194,12 @@ module DL return ptr end - def handler - ``` @handler or raise "call dlload before importing symbols and ``` functions" - end - def import\_symbol(name) - ``` addr = @handler.sym(name) ``` - ``` addr = handler.sym(name) if( !addr ) raise(DLError, "cannot find the symbol: #{name}") end ``` @@ -203,7 +207,7 @@ module DL end ``` def import_function(name, ctype, argtype, call_type = nil) ``` - ``` addr = @handler.sym(name) ``` - ``` addr = handler.sym(name) if( !addr ) raise(DLError, "cannot find the function: #{name}()") end ``` ---
**Author:** ![Aston](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/85f322/32.png) [@Aston](https://www.ruby-forum.com/u/Aston)\ **Post date:** [July 6, 2010, 1:38am UTC](https://www.ruby-forum.com/t/ruby-dl-problem/191015/6 "2010-07-06T01:38:15Z")
On Sun, Jul 04, 2010 at 10:02:28AM +0900, Nobuyoshi N. wrote: > The following patch refines the error messages. I like this, so I’ve added it. Thanks Nobu!