Ruby cmd line script executes code non-consecutively

Question

I've built a ruby script that is supposed to run in the terminal.

$ ruby script.rb

I have some code specific to newer versions of ruby so I added a ruby version check towards the top of the page:

abort("You're using ruby #{RUBY_VERSION}. Please use version 2.1 or newer") if (RUBY_VERSION.to_f < 2.1)

I double checked the code line in irb and seems to work when changing the ruby version via RVM.

However, when I run the ruby script file under, say ruby 1.8.7, the script blows up with the following error:

$ ruby script.rb 
script.rb:6: odd number list for Hash
option1:            'some options',
        ^
script.rb:6: syntax error, unexpected ':', expecting '}'
option1:            'some options',
        ^
script.rb:6: syntax error, unexpected ',', expecting $end

This would be expected behavior if I didn't have the version check on the top of the file.

Why doesn't the version check execute before the next lines of code? Is there a way to force execution of the ruby check before continuing with the rest of the code?

My full file is:

#!/usr/bin/env ruby

abort("You're using ruby #{RUBY_VERSION}. Please use version 2.1 or newer") if (RUBY_VERSION.to_f < 2.1)

options = {
    option1: 'some options',
    option2: 'some more options',
    option3: 'other options'
}

infused · Accepted Answer · 2015-05-05 21:54:56Z

5

That error is on the ruby parser. In ruby 1.8.7 hashes with symbols must be written with hashrockets { :option => 'some options'} because the shorthand { option: '' } was only introduced in ruby 1.9

To explain it better, ruby has to parse the whole file before executing anything on it. So your version check wont be executed because your file has invalid ruby 1.8 syntax.

edited May 5, 2015 at 21:54

infused

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answered May 5, 2015 at 21:37

Ismael

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1 Comment

Myst Over a year ago

It's possible to separate the code into two files. Moving the code to an external files called actual_script.rb, it should be possible to use load 'actual_script.rb' after the version check... maybe you can add that in the answer, for future reference?

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