nickanderson

CFEngine manage Xscreensaver mode

This example implements search and replace in a file (specifically an Xresources formatted file).

bundle agent __main__
{
  methods:
      "Test data"
        usebundle => init_test_file( $(example.file) );

nickanderson

Using getuid() to get a users uid avoiding error from call where user does not exist

A question from Wolfgang in #CFEngine:matrix.org

I’m confused. I have a bundle that should only run on one specific host. What confuses me is that CFE tries to evaluate the variables. In that bundle, I have something like “uid” int => getuid(“my-user”), but of course this user does not exist on the other systems. However, cfe shows an error saying that it could not get the uid for that user.

CFEngine is eager to resolve variables (classes in common bundles too), for more read about pre-evaluation.

nickanderson

You can use $(const.dollar) if you are looking to render a literal $( ) into a file, alternatively you can use backticks.

bundle agent example_subshell_cfengine_files_promise
{
  files:
      "/tmp/using-const.dollar.txt"
        content => "#!/bin/env bash $(const.n)echo $(const.dollar)(hostname)",
        perms => m( "u+rwx" );

nickanderson

Example for tangling the same content to different places based on header arguments

nickanderson

Bundle parameters are optional.

Both in the sense of implementation, but also from the perspective of use.

I did not know (or if I did, i don’t even remember forgetting) that bundle parameters, if present are optional. In that, a bundle that has parameters can be called without parameters . However, if you call with non-zero parameters you must supply all (that part I knew).

bundle agent __main__
{

nickanderson

bundle agent __main__
{
  vars:
      "stuff" slist => { "some", "thing-s", "that's", "not valid", "variable names"};

      "classic_associative_array[$(stuff)]"
        string => string_upcase("$(stuff)");
}

nickanderson

bundle agent php
{
	vars:
		"version" string => ifelse( "debian.!ubuntu", "8.0",
                                          "ubuntu", "8.2",
                                          "centos", "8.3",
                                          "freebsd", "82",
                                           " ¯\_(ツ)_/¯" );

nickanderson

variablesmatching_as_data() is useful for centralizing information from disparate sources. For example, deriving a list of package names by extracting the values from variables that match a specific name.

 bundle agent package_names_from_variablesmatching_as_data
 # @brief Example illustrating deriving a list of package names from variables named with a specific naming convention
{
  vars:
      "packages_baseline" slist => { "bash-completion", "emacs" };
      "packages_os" slist => { "httpd" };

nickanderson

@nickanderson The title piqued my interest so I had a read. Bearing in mind that I don't use cfengine,
so it's likely my fault for not understanding, but I would have liked to see how you do different
things _as_a_result_ of the different repaired vs kept vs reached scenarios.

Is it possible to do that? Say create a new file with contents that vary based on which of those
scenarios occured?

Thanks!

nickanderson

bundle agent __main__
{

    vars:
    "repo_data" data => '{"one": { "value": "something" }, "two": { "run_class": "linux" } }';
    "repo_names" slist => getindices(repo_data);
    reports:
          "$(this.bundle): yes or/not $(repo_names)"
              if => or(