Do you know how to use every function available in CFEngine?
Join Cody, Craig, Herman to see how Nick uses org-mode, org-roam, and ob-cfengine3 to manage his personal collection of CFEngine Function Examples.
Video
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Notes
Live coded examples for the following functions:
regline( regex, filename )- Returns whether the anchored regular expression
regexmatches a line infilename.
- Returns whether the anchored regular expression
reglist( list, regex )- Returns whether the anchored regular expression
regexmatches any item inlist.- Very similar to
some( regex, list )but it differs in reversed parameters and the regular expression is unanchored.
- Very similar to
- Returns whether the anchored regular expression
parseyaml( 'inline-yaml' )- Parses YAML data directly from a string and returns the result as a data variable.
- Not to be confused with
readyaml()which is for parsing a YAML file, a much more common use case.
- Not to be confused with
- Parses YAML data directly from a string and returns the result as a data variable.
regline()
Look to see if quiet is a boot option.
bundle agent __main__
{
classes:
"have_quiet_boot"
expression => regline("$(anchored_regex)", $(file));
vars:
# e.g. BOOT_IMAGE=/vmlinuz-5.15.0-52-generic root=/dev/mapper/vgkubuntu-root ro quiet splash vt.handoff=7
"anchored_regex"
string => ".*\s+quiet\s*.*";
"file"
string => "/proc/cmdline";
reports:
have_quiet_boot::
"Have quiet in body cmdline args";
"$(file)" printfile => cat($(file));
}R: Have quiet in body cmdline args
R: /proc/cmdline
R: BOOT_IMAGE=/vmlinuz-5.15.0-52-generic root=/dev/mapper/vgkubuntu-root ro quiet splash vt.handoff=7reglist()
Determine if at least one element of a list starts with c (case insensitive).
bundle agent __main__
{
vars:
"names"
slist => {"Cody", "Craig", "Herman", "Nick"};
# This regex is unanchored, because the function itself anchors it.
"anchored_regex"
string => "(?i)c.*";
reports:
# Emit report if at least one element starts with c or C
"$(this.namespace):$(this.bundle).names has at least one element matching '$(anchored_regex)'"
if => reglist(names, $(anchored_regex));
"names: $(with)"
with => join(", ", names);
}R: default:main.names has at least one element matching '(?i)c.*'
R: names: Cody, Craig, Herman, Nickparseyaml()
Demonstrate how to parse inline YAML and access different parts of the data structure.
bundle agent __main__
{
vars:
"some_yaml"
data => parseyaml('
mykey: myvalue
domain:
name: example.com
subdomain: asdf
nesting:
levelzero:
levelone: levelone');
"top_level_keys"
slist => getindices(some_yaml);
"nesting_keys"
slist => getindices("some_yaml[nesting]");
"nesting_levelzero_keys"
slist => getindices("some_yaml[nesting][levelzero]");
reports:
"$(with)"
with => storejson(some_yaml);
}R: {
"domain": {
"name": "example.com",
"subdomain": "asdf"
},
"mykey": "myvalue",
"nesting": {
"levelzero": {
"levelone": "levelone"
}
}
}
Variable name Variable value Meta tags Comment
default:main.nesting_keys {"levelzero"} source=promise
default:main.nesting_levelzero_keys {"levelone"} source=promise
default:main.some_yaml {"domain":{"name":"example.com","subdomain":"asdf"},"mykey":"myvalue","nesting":{"levelzero":{"levelone":"levelone"}}} source=promise
default:main.top_level_keys {"mykey","domain","nesting"} source=promiseNote: In the above example output, the cf-agent was executed with --show-evaluated-vars=main\. which outputs variables, their values, tags, and comments.
Links
- Org-roam A plain-text personal knowledge management system https://www.orgroam.com/
- Org-mode A GNU Emacs major mode for keeping notes, authoring documents, computational notebooks, literate programming, maintaining to-do lists, planning projects, and more - in a fast and effective plain text system https://orgmode.org/
- ob-cfengine3 Execute CFEngine policy within org-mode https://github.com/nickanderson/ob-cfengine3
- Spacemacs a community driven Emacs distribution https://www.spacemacs.org/
- CFEngine Spacemacs Layer https://develop.spacemacs.org/layers/+tools/cfengine/README.html
- Documentation for
regline()https://docs.cfengine.com/docs/master/reference-functions-regline.html - Documentation for
reglist()https://docs.cfengine.com/docs/master/reference-functions-reglist.html - Documentation for
some()https://docs.cfengine.com/docs/master/reference-functions-some.html - Documentation for
parseyaml()https://docs.cfengine.com/docs/master/reference-functions-parseyaml.html - Documentation for
readyaml()https://docs.cfengine.com/docs/master/reference-functions-readyaml.html - Connect on LinkedIn w/ Cody, Craig, Herman, or Nick
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