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GNU cfengine

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3.4.3 shellcommand classes

For more advanced uses of cfengine you might want to be able to define a class on the basis of the success or failure of a user-program, a shell command or user script. Consider the following example

 
groups:

   have_cc = ( "/bin/test -f /usr/ucb/cc" 
               "/bin/test -f /local/gnu/cc"  )

Note that as of version 1.4.0 of cfengine, you may use the word classes as an alias for groups. Whenever cfagent meets an object in a class list or variable, which is surrounded by either single, double quotes or reversed quotes, it attempts to execute the string as a command passed to the Bourne shell. If the resulting command has return code zero (proper exit) then the class on the left hand side of the assignment (in this case `have_cc') will be true. If the command returns any other value (an error number) the result is false. Since groups are the logical OR of their members (it is sufficient that one of the members matches the current system), the class `have_cc' will be defined above if either `/usr/ucb/cc' or `/local/gnu/cc' exist, or both.


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