On Tue, Aug 25, 2009 at 9:00 AM, David Schmitt<[email protected]> wrote:
>
> Thomas Bellman wrote:
>> Allan Marcus wrote:
>>
>>> This has probably been discussed, but I would like an exec to only be
>>> executed if a facter variable is true. Seems there are two ways of
>>> doing this, but I can only get the "if" way to work.
>>>
>>> # $lanl_sav_defdate is a custom fact
>>> # make sure the live update file is correct, then force a liveupdate
>>> class forceLiveupdate {
>>> if $lanl_sav_defdate == 'February13,2008'{
>>> # execute the live update command
>>> exec {"liveupdate-now":
>>> command => "[long command omited]",
>>> }
>>> }
>>> }
>>
>> That is the easiest way.
>>
>>> Is this the "right" way of using a conditional, or should I use an
>>> onlyif? Something like this, which doesn't seem to work for me:
>>>
>>> class forceLiveupdate {
>>> # execute the live update command
>>> exec {"liveupdate-now":
>>> command => "[long command omited]",
>>> onlyif => "match $lanl_sav_defdate == 'February13,2008'",
>>> }
>>> }
>>
>> The 'onlyif' and 'unless' parameters are shell commands, whose exit status
>> determines if the shell command in the 'command' parameter will be run.
>> Neither my CentOS, Fedora, Gentoo nor Solaris machines have a command named
>> 'match', so that would return non-zero, and your command will not be run.
>>
>> A working version would rather use
>>
>> onlyif => "[ '$lanl_sav_defdate' = 'February13,2008' ]"
>>
>> However, there are several problems with this. First of all, you will have
>> worse performance, since it will involve a fork() and exec(), which aren't
>> the cheapest things one can do. Second, you have quoting problems; if your
>> lanl_sav_defdate happens to contain a single quote, you will have problems.
>> (In the upcoming 0.25 there is a function 'shellquote()' which can help you
>> with that.)
>>
>> On the other hand, if you have requires or subscribes elsewhere that points
>> to Exec[liveupdate-now], then those won't work if you wrap the exec in an
>> if statement.
>
> There is an easy workaround for the last problem: define an exec with
> /bin/true in the else-branch:
>
> | exec { "liveupdate-now":
> | command => "/bin/true # fake",
> | }
>
> This allows one to ignore wether or not the exec is "active".
I've done this like this in the past:
exec { "my_command":
command => $some_variable ? {
"true" => "blah blah some real command",
"false" => "/bin/true",
}
}
but it always feels hacky.
--
Nigel Kersten
[email protected]
System Administrator
Google, Inc.
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