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4513

answers:

5

Hello!

I need ERB (Ruby's templating system) for templating of non-HTML files.
(Instead, I want to use it for source files such as .java, .cs, ...)

How do I "execute" Ruby templates from command line?

+2  A: 

You should have everything you need in your ruby/bin directory. On my (WinXP, Ruby 1.8.6) system, I have ruby/bin/erb.bat

erb.bat [switches] [inputfile]
  -x               print ruby script
  -n               print ruby script with line number
  -v               enable verbose mode
  -d               set $DEBUG to true
  -r [library]     load a library
  -K [kcode]       specify KANJI code-set
  -S [safe_level]  set $SAFE (0..4)
  -T [trim_mode]   specify trim_mode (0..2, -)
  -P               ignore lines which start with "%"

so erb your_erb_file.erb should write the result to STDOUT.

(EDIT: windows has erb.bat and just plain "erb". The .bat file is just a wrapper for erb, which I guess should make the same command work pretty much the same on any OS)

See the prag prog book discussion (starts about half-way down the page).

Note also that Jack Herrington wrote a whole book about code generation that uses Ruby/ERB.

Mike Woodhouse
Great! I **was** trying to run erb (without knowing if it's correct) but failed, so I thought that it can't be done directly, but need some external library instead. After your reply I realized, that I only had a custom ruby installed, which wasn't in system's path ;) Thank you!
ivan_ivanovich_ivanoff
I need it for an ant script (it has to run on all platforms). I noticed that here under linux I have erb (without extension), but you've mentioned erb.bat (so I assume under windows you don't have erb without extension). Can you suggest me how to start erb in a multi-platform way?
ivan_ivanovich_ivanoff
+2  A: 

Write a ruby script that does it. The API documentation is here: http://www.ruby-doc.org/stdlib/libdoc/erb/rdoc/

For example:

template = ERB.new File.new("path/to/template.erb").read, nil, "%"
template.result(binding)

(Where binding is a binding with the @vars that the template needs.)

Sam
A: 

Another option would be to use ruby -e, since ERB itslef is so simple.

Something like:

ruby -rerb -e "puts ERB.new(File.read(<file name here>)).result"

However, I assume you have a context you want to render the template in. How are you expecting to get that context? As an example, check out:

ruby -rerb -e "hello = 'hello'; puts ERB.new('<%= hello %> world').result(binding)"

which will print out "hello world", using the top-level, where you defined the hello variable, as the binding.

Yehuda Katz
A: 

I tried to comment on this, but comments link not available.

I'm using this:

template = ERB.new File.new("path/to/template.erb").read, nil, "%"
template.result(binding)

From the posting above: and I found what I think it might be a problem:

I'm creating DOS BATCH files like:

%JAVA_HOME%\bin\jar -xvf <%=inputfile%>...

And I found weird thing problem - I get this when I run with the code above:

Processing Template test.txt
erb):2:in `render': compile error (SyntaxError)
erb):2: syntax error, unexpected tSTRING_BEG, expecting $end
erbout.concat "\n"
               ^
       from DBUser.rb:49:in `render'
       from DBUser.rb:43:in `each'
       from DBUser.rb:43:in `render'
       from DBUser.rb:81

I tried the following, and got round my particular problem - not sure if this is the right answer for everybody ...

template = ERB.new File.new("path/to/template.erb").read
template.result(binding)
monojohnny
+1  A: 

If you can switch ERB to Erubis, your problem solving is as simple as:

require 'erubis'
template = File.read("sample_file.erb")
template = Erubis::Eruby.new(template)
template.result(:your_variable => "sample")