# More mono problems

**URL:** <https://www.ruby-forum.com/t/more-mono-problems/156656>\
**Category:** IronRuby\
**Created:** [December 31, 2008, 2:02pm UTC](https://www.ruby-forum.com/t/more-mono-problems/156656 "2008-12-31T14:02:10Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![barby](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/b/c57346/32.png) [@barby](https://www.ruby-forum.com/u/barby)\
**Post date:** [December 31, 2008, 2:02pm UTC](https://www.ruby-forum.com/t/more-mono-problems/156656/1 "2008-12-31T14:02:10Z")

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It looks like IronRuby doesn’t want to function properly on mono.

I can’t run an external file for example. I created a file with as  
content 1

- 1 and when I run that file I get the following error:

» mono ir.exe -D test.rb  
mscorlib:0:in `set_Fallback': Argument cannot be null. (System::ArgumentNullException) from mscorlib:0:in`.ctor’  
from mscorlib:0:in `GetDecoder' from mscorlib:0:in`Initialize’  
from mscorlib:0:in `.ctor' from mscorlib:0:in`.ctor’

I can run the console and do 1 + 1 without a problem but then it doesn’t  
display the result =\> 2 just a new prompt

» mono ir.exe -D  
IronRuby 1.0.0.0 on .NET 2.0.50727.1433  
Copyright © Microsoft Corporation. All rights reserved.

Note that local variables do not work today in the console.  
As a workaround, use globals instead (eg $x = 42 instead of x = 42).

> > > 1 + 1  
> > > puts “hello world”  
> > > hello world

When I try to require something like rubygems I get the same error as  
when I  
try to run a file. I’m guessing this is a mono issue.  
I changed the paths in ir.exe.config to the correct ones.

» mono ir.exe -D  
IronRuby 1.0.0.0 on .NET 2.0.50727.1433  
Copyright © Microsoft Corporation. All rights reserved.

Note that local variables do not work today in the console.  
As a workaround, use globals instead (eg $x = 42 instead of x = 42).

> > > require ‘rubygems’  
> > > mscorlib:0:in `set_Fallback': Argument cannot be null. (System::ArgumentNullException) from mscorlib:0:in`.ctor’  
> > > from mscorlib:0:in `GetDecoder' from mscorlib:0:in`Initialize’  
> > > from mscorlib:0:in `.ctor' from mscorlib:0:in`.ctor’  
> > > from IronRuby.Libraries:0:in `require’