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I already found some examples where I can check if a variable has a specific value

if $var == 'somevalue' {

of if something is defined

if defined(Package['somepackage']) {

but how can I check if a user exists and fail if it doesn't. It would be sufficient to know how to use the result of a script or shell test because /usr/bin/id -u ${name} >/dev/null 2>&1 is all I need, even a check if the user directory exists would be ok.

file and exec do not accept the onlyif parameter, otherwise this wouldn't be a problem at all

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An what if you just use ensure parameter of user? – m0nhawk Jan 24 '13 at 8:46
would that just fail if the user doesn't exist or would it try to create that user? – Dehalion Jan 24 '13 at 8:50
I think if you set ensure=present it would create user and do nothing if the user exist. – m0nhawk Jan 24 '13 at 8:51
OK, that was what I thought/was afraid of. I don't want to create a user, i just want to do some things if it exists. Thanks anyway, found something else useful in the puppet reference you linked. But my main problem remains... – Dehalion Jan 24 '13 at 8:56
And what about using require => User['foo'], for what you want to do? – m0nhawk Jan 24 '13 at 8:58

Why not just add in a facter fact and check on it?

with my setup on puppet 3, I'd place the following into modules/facts/lib/facter/user_exists_blah.rb

require 'facter'
Facter.add(:user_exists_blah) do
  setcode do
    name = "blah"
    Facter::Util::Resolution.exec("/usr/bin/id -u #{name} 2>/dev/null")

And then use it as

if $::user_exists_blah {

An empty string evaluates to false, so you can just use it as a boolean

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That looks like what I want to do. Is it also possible to parametrize this facter (give the user name as a parameter)? – Dehalion Jan 27 '13 at 21:05
Sadly AFAIK, no, you can't – kormoc Jan 27 '13 at 22:25
You can have a Facter fact return all the users on the system, though, and have the master make decisions based on that. – jgoldschrafe Feb 3 '13 at 6:20
That's actually a really good point jgoldschrafe! Thanks for that insight. – kormoc Feb 4 '13 at 7:52
You implementation always returns an empty string. I changed the command to "/usr/bin/id -u #{name} 2>/dev/null". Now the variable $user_exists_blah in the if-statement is truthy (non empty string containing the uid) or falsy (an empty string). – geekQ May 30 '13 at 19:24

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