writing custom fact -> return value not as expected

[Denny]

Hi there,

probably a pretty easy to answer question.

I want to try out adding custom facts. My first custom fact should be "lastrebootdate"

My code looks like this:

Facter.add(:lastrebootdate) do

  setcode do

    Facter::Util::Resolution.exec("/usr/bin/who -b |awk '{print $3}'")

  end

end

Running the command on the system returns "2017-01-30"

Deploying my fact on a puppet node and running the puppet agent returns "Jan".

$ puppet facts |grep lastrebootdate

    "lastrebootdate": "Jan",

What did I miss?

Thank you,

Denny

[Denny]

PS: I'm running facter 3.5.0 with puppet 4.8.1 on CentOS 7

[Denny]

Tried out another customfact "lastyumupdate" which looks like:

Facter.add(:lastyumupdate) do

  setcode do

    Facter::Util::Resolution.exec("yum history |grep -E '^.*(Update| U).*$' |head -n 1 |awk '{print $6}'")

  end

end

This one returns on command line "2017-01-10" AND sets the fact correct

$ puppet facts |grep last

    "lastrebootdate": "Jan",

    "lastyumupdate": "2017-01-10",

Any help is appreciated :)

Denny

[Rob Nelson]

At a guess, dollar signs inside double quotes interpolate, so it's extremely possible that somewhere earlier in the ruby run, $3 matched "Jan" somewhere and that was reused in your awk command. In the latter usage there's probably no $6 (that's a lot of matches!) or it amazingly has the value '$6'. I would definitely be more careful about escaping any dollars inside of double quoted strings that are passed to exec(), system(), or similar functions, as escaping that can be a nightmare when the stars align during your design but not weeks later during your usage.

[Stefan Schulte]

Hi Denny,

IIRC facter will internally run commands with a C locale to get reliable
command output on different locale settings [1]

% LC_ALL=de_DE.utf8 /usr/bin/who -b |awk '{print $3}'
19:34
% LC_ALL=en_US.utf8 /usr/bin/who -b |awk '{print $3}'
2017-01-10
% LC_ALL=C /usr/bin/who -b |awk '{print $3}'
Jan

[1] https://github.com/puppetlabs/facter/pull/696

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[Stefan Schulte]

Hey Rob,

variable interpolation in strings in ruby is actually done with
#{some_var}, so the following snippet

#!/usr/bin/ruby

"Hello World".match(/Hello (.*)/)

puts $1
puts "$1"
puts "#{$1}

actually returns

World
$1
World

As you can see "$1" does not interpolate to an earlier match.

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[Rob Nelson]

Thanks for the correction. Definitely way off base on that, my apologies for the erroneous claims!

Rob Nelson
rnel...@gmail.com

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[Dirk Heinrichs]

Am 10.01.2017 um 22:29 schrieb Stefan Schulte:

% LC_ALL=de_DE.utf8 /usr/bin/who -b |awk '{print $3}'

19:34

% LC_ALL=en_US.utf8 /usr/bin/who -b |awk '{print $3}'

2017-01-10

Interesting. On my system, there's no difference between them (left out the awk part for clarity):

% LC_ALL=en_US.UTF-8 who -b
         system boot  2017-01-02 11:10
% LC_ALL=de_DE.UTF-8 who -b
         system boot  2017-01-02 11:10

% LC_ALL=C /usr/bin/who -b |awk '{print $3}'

Jan

Only here:

% LC_ALL=C who -b
         system boot  Jan  2 11:10

Bye...

    Dirk

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[Denny]

Thank you guys for the clarification!

Stupid question #2:

How do I get facter use LC_ALL=en_US.UTF-8 instead of LC_ALL=C?

A simple add to my Facter::Util::Resolution.exec("...") did not work, of course.

Denny

[Thomas Müller]

Am Dienstag, 10. Januar 2017 17:44:23 UTC+1 schrieb Denny:

Hi there,

probably a pretty easy to answer question.

I want to try out adding custom facts. My first custom fact should be "lastrebootdate"

My code looks like this:

Facter.add(:lastrebootdate) do

  setcode do

    Facter::Util::Resolution.exec("/usr/bin/who -b |awk '{print $3}'")

  end

end

Running the command on the system returns "2017-01-30"

just a random thought: instead of calling who you could take the already existing uptime fact and just calculate the date with ruby time/date functions.

- Thomas
 

[Rob Nelson]

There's also `last reboot -1`, add your favorite timestamp format with -T :)

Rob Nelson
rnel...@gmail.com

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