Puppet Function: getvar_emptystring

Defined in:
lib/puppet/parser/functions/getvar_emptystring.rb
Function type:
Ruby 3.x API

Overview

getvar_emptystring(String $variable) ⇒ String

Return a variable in a remote namespace, but returns an empty string if the variable is undefined or can’t be found. This is useful when trying to lookup a value that might be undefined on first run, like a fact for an application that will be installed as part of a Puppet run, but you don’t want the reference to an undefined variable to cause an error when strict variables are enabled.

Examples:

Checking a variable exists (Equivalent to $foo = $site::data::foo)

$foo = getvar('site::data::foo')

Calling the function. (Equivalent to $bar = $site::data::bar)

$datalocation = 'site::data'
$bar = getvar("${datalocation}::bar")

Combining with the pick() function

$redis_version_real = pick(getvar_emptystring('redis_server_version'), '3.2.1')

Parameters:

  • variable (String) —

    The variable to lookup

Returns:

  • (String) —

    The value of the variable if found

  • (String) —

    An empty string if the variable is not found eg. ‘”`



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# File 'lib/puppet/parser/functions/getvar_emptystring.rb', line 3

newfunction(:getvar_emptystring, :type => :rvalue, :doc => <<-DOC
Return a variable in a remote namespace, but returns an empty
string if the variable is undefined or can't be found.
This is useful when trying to lookup a value that might be undefined
on first run, like a fact for an application that will be installed as
part of a Puppet run, but you don't want the reference to an undefined variable
to cause an error when strict variables are enabled.
@param variable [String] The variable to lookup
@return [String] The value of the variable if found
@return [String] An empty string if the variable is not found eg. `''`
@example Checking a variable exists (Equivalent to $foo = $site::data::foo)
$foo = getvar('site::data::foo')
@example Calling the function. (Equivalent to $bar = $site::data::bar)
$datalocation = 'site::data'
$bar = getvar("${datalocation}::bar")
@example Combining with the pick() function
$redis_version_real = pick(getvar_emptystring('redis_server_version'), '3.2.1')
DOC
) do |args|

  unless args.length == 1
    raise Puppet::ParseError, ("getvar_emptystring(): wrong number of arguments (#{args.length}; must be 1)")
  end

  begin
    result = self.lookupvar("#{args[0]}")

    result = '' if result.nil?

    result
  rescue Puppet::ParseError # Eat the exception if strict_variables = true is set and return an empty string
    return ''
  end

end