When you want to inspect both the return code and output from a command execresult_as_data() might be the function you are searching for. Most CFEngine policy writers have used execresult() and returnszero(). They are useful when you want to do something based on the output of a command or based on its successful execution (returning zero). For example: /tmp/feature-friday-3.cf command output But, sometimes, you care about specific return codes.

Ever wanted to manipulate a string - temporarily - for an individual promise? Check out the with attribute and its special, $(with) variable. Sometimes you need some variation on a string for a specific case. Traditionally, to achieve this you’d simply define another variable. Here is a contrived example: I have a string, nginx and I want to emit a report that contains both the string itself and the upper case version of the string.

Looking for a way to concisely set a variable conditionally? Have you heard of ifelse()? In CFEngine, traditionally class expressions are used to constrain promises to different contexts. Setting a variable to different values based on context might look like this: /tmp/feature-friday-1.cf command output That’s great, lots of flexibility, but with an increasing number of options the policy can get quite long and it’s easier for a human interpreter to lose track of the context.