How can I put the output of a Chef 'execute resource' into a variable

Question

I'd like to put the output of a shell command into a variable for later use in a Chef recipe.

In bash I could do something like output=`tail -1 file.txt` and then I could echo $output

Can an 'execute resource' do this so that I can use the result later in the recipe?

score 20 · Answer 1 · edited Apr 17 '18 at 15:46

20

while Graham's solution seemed to work at first, I found out about Chef::Mixin:ShellOut

ruby_block "check_curl_command_output" do
    block do
      #tricky way to load this Chef::Mixin::ShellOut utilities
      Chef::Resource::RubyBlock.send(:include, Chef::Mixin::ShellOut)      
      curl_command = 'curl --write-out %{http_code} --silent --output /dev/null '+node['url']
      curl_command_out = shell_out(curl_command)
      if curl_command_out.stdout == "302"
        ...
      else
        ...
      end
    end
    action :create
end

Chef::Mixin:ShellOut is particularly useful if you need to run the command as a specific user (cf. http://www.slideshare.net/opscode/chef-conf-windowsdougireton ):

ruby_block "run_command_as" do
    block do
    Chef::Resource::RubyBlock.send(:include,Chef::Mixin::ShellOut)
    add_group = shell_out("your command",
        {
          :user => "my_user",
          :password => "my_password",
          :domain => "mycorp.com"
        }
        )
    end
end

edited Apr 17 '18 at 15:46

guido

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answered Dec 16 '13 at 14:27

Francois

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This is a more elegant solution to the problem than the accepted answer, and provides better functionality. Thanks for posting, Francois! – cixelsyd Jul 03 '14 at 21:07
Is there anybody who wrote chefspec for this type of code? – Joel Handwell Dec 28 '15 at 23:18
Loading the shell_out helper manually into resources/providers is no longer necessary, and there's no need for the indirection with the ruby_block in this case. The simple one-liner below is a much better solution to start with. – lamont Aug 21 '20 at 01:41

score 3 · Answer 2 · edited Aug 21 '20 at 01:42

3

Works for me

passenger_root = shell_out("passenger-config --root").stdout

edited Aug 21 '20 at 01:42

lamont

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answered Jul 04 '18 at 13:03

Aivils Štoss

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The `require 'chef/mixin/shell_out'` line is no longer necessary. This should also really be the accepted answer. There's no need to use the ruby_block or to inject the shell_out methods any longer. (And i just updated the answer to remove the require line) – lamont Aug 21 '20 at 01:38

How can I put the output of a Chef 'execute resource' into a variable

2 Answers2

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