Create a Custom function in puppet

Question

Could somebody specify how to create a new custom function in puppet?

Answer 1

All the custom functions are implemented as separate .rb files and are distributed among modules. 

One needs to put custom functions in lib/puppet/parser/function.

Creating a New Function :

New functions are created or defined using the newfunction method inside the puppet::parser::Functions module. 

One needs to pass the function name as a symbol to newfunction method and the code to run as a block. 

The following example is a function, which is used to write a string to the file inside the /user directory.

module Puppet::Parser::Functions 
   newfunction(:write_line_to_file) do |args| 
      filename = args[0] 
      str = args[1] 
      File.open(filename, 'a') {|fd| fd.puts str } 
   end 
end

Once the user has the function declared, it can be used in the manifest file as shown below.

write_line_to_file('/user/Sam.txt, "Hello Sam!")