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Ruby error

Posted on 2011-09-06
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Last Modified: 2012-05-12
I'm getting the following error message when trying to run a ruby script.  I listed the beginning of the script for reference.  Please help.


<internal:lib/rubygems/custom_require>:29:in `require': no such file to load -- exceptions (LoadError)
        from <internal:lib/rubygems/custom_require>:29:in `require'
        from ./ssh_helpers.rb:6:in `<main>'

-------------------------SCRIPT IS BELOW-------------------------------------

#!/usr/bin/env ruby
require 'rubygems'
require 'open4'
require 'socket'

require 'exceptions'


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Question by:johncosentino
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Expert Comment

by:Andrew Doades
ID: 36489058
Its this line that's causing the issue:

require 'exceptions'

What are you trying to require? is this a gem or a separate ruby file?

Andrew
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Expert Comment

by:Andrew Doades
ID: 36489064
To Clarify what the error message is, its trying to explain, it doesn't know what 'exceptions' is - it isn't an installed gem, nor is there an 'exceptions.rb' file in the same directory as this script
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Author Comment

by:johncosentino
ID: 36489135
This is a separate ruby file, and I confirmed that the exceptions.rb file is in the same directory as the script in question.
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Author Comment

by:johncosentino
ID: 36490295
So I've found a fix, though I'm still not sure what causes the problem.

if you change the line in the script from require 'exceptions' to require_relative 'exceptions' the problem is resolved.

Apparently the "_relative" tells the script to look in the current directory?  
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Expert Comment

by:Andrew Doades
ID: 36490326
The only thing I can think off, is that ruby is trying to use system call with it being 'exceptions'?
One other thing you could try would be to rename the file to 'my_exceptions.rb' and then
require 'my_exceptions'

By using _relative you're forcing ruby to check the current directory first.

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Author Comment

by:johncosentino
ID: 36490361
This might be a stupid question, but why wouldn't it check the current directory first with just "require"....what does "require" check first?
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Expert Comment

by:Andrew Doades
ID: 36490382
Are you running this script from within the directory its located?

Have you done something like this:
cd /ruby_files/
ruby test.rb

So when you run the ruby file, you're running it from the same directory?

or are you running it like this:
ruby ruby_files/test.rb
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Accepted Solution

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JESii earned 500 total points
ID: 36492615
ruby sets up a number of directories that it looks in for locating files that are required.  You can see what that is on your system by typing:
   ruby -e 'puts $:'
(The $: is a global variable that contains the load paths for load / require expressions)

It's kind of a linux convention to not  automatically look in the current directory; this avoids the scenario where someone puts a malicious file in your current directory to has the same name as another command and therefore gets executed when you run that command. That's why in Linux (or Mac Terminal), you have to type:
   ./command_name
to run something from the current directory.

And that's why there's require_relative... to make it easier to access the current directory for loaded or required files.
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