How to run a task when variable is undefined in ansible

Question

I am looking for a way to perform a task when ansible variable is not registers  undefined e g   -- name  some task    command   sed -n  5p     app dirs includes   BUILD info    awk   print   2      when     deployed revision  AND    deployed revision stdout      register  deployed revision

User · Accepted Answer

From the ansible docs  If a required variable has not been set  you can skip or fail using Jinja2   s defined test  For example   tasks   - shell  echo  I ve got     foo     and am not afraid to use it     when  foo is defined  - fail  msg  Bailing out  this play requires  bar     when  bar is not defined   So in your case  when  deployed revision is not defined should work

User · Answer

As per latest Ansible Version 2 5  to check if a variable is defined and depending upon this if you want to run any task  use undefined keyword   tasks      - shell  echo  I ve got     foo     and am not afraid to use it         when  foo is defined      - fail  msg  Bailing out  this play requires  bar         when  bar is undefined   Ansible Documentation

User · Answer

Strictly stated you must check all of the following  defined  not empty AND not None   For  normal  variables it makes a difference if defined and set or not set  See foo and bar in the example below  Both are defined but only foo is set   On the other side registered variables are set to the result of the running command and vary from module to module  They are mostly json structures  You probably must check the subelement you re interested in  See xyz and xyz msg in the example below   cat  gt  test yml  lt  lt EOF - hosts  127 0 0 1    vars      foo                foo is defined and foo       and foo    None     bar                bar is defined and bar       and bar    None    tasks     - debug        msg          register  xyz      xyz is defined and xyz       and xyz    None                        xyz msg is defined and xyz msg       and xyz msg    None    - debug        msg   foo is defined and foo       and foo    None      when  foo is defined and foo       and foo    None    - debug        msg   bar is defined and bar       and bar    None      when  bar is defined and bar       and bar    None    - debug        msg   xyz is defined and xyz       and xyz    None      when  xyz is defined and xyz       and xyz    None   - debug        msg      xyz        - debug        msg   xyz msg is defined and xyz msg       and xyz msg    None      when  xyz msg is defined and xyz msg       and xyz msg    None   - debug        msg      xyz msg     EOF ansible-playbook -v test yml

[ansible] How to run a task when variable is undefined in ansible?

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