How can I use regex in when condition - regex

Question

On an Ansible playbook, I'm trying to execute a shell command only if a service exist on the remote server.
I have 3 tasks :
service_facts
execution of shell command if tomcat is installed
display the output of the shell command if tomcat is installed
Here is my code :
- name: Get Infos
hosts: all
gather_facts: yes
become: false
remote_user: [MY_USER]
tasks:
- name: Get the list of services
service_facts:
- name: Get version of Tomcat if installed
become: true
shell: 'java -cp /opt/tomcat/lib/catalina.jar org.apache.catalina.util.ServerInfo | grep "Server version"'
register: tomcat_version
when: "'tomcat.service' in services"
- debug: msg="{{ tomcat_version.stdout_lines }}"
when: "'tomcat.service' in services"
The problem is on certains servers the service name is, for example, tomcat-8.1
How can i use regex in the when condition?
I tried regex(), regex_search(), either I'm doing it wrong or I don't know how to do it.
Have you any idea how to do it?
Thanks in advance!

Answer 1

Count matching items. For example
- service_facts:
- block:
- shell: smartctl --version | head -1
register: smart_version
- debug:
msg: "{{ smart_version.stdout_lines }}"
when: _srvcs|length > 0
vars:
_regex: '.*smart.*'
_srvcs: "{{ services|select('match', _regex) }}"
gives
msg:
- smartctl 7.1 2019-12-30 r5022 [x86_64-linux-5.4.0-73-generic] (local build)
The next option is to intersect the list of services, e.g.
when: _srvcs|length > 0
vars:
my_services:
- smartmontools.service
- smart-8.1
- smart-devel.0.0.1
_srvcs: "{{ my_services|intersect(services) }}"
Debug
Q: "It gives me a failure on the server where my service doesn't exist, cause the playbook still tries to execute the shell. Is it normal?"
A: No. It is not normal. Print debug and find out why the condition evaluates to true, i.e. what service(s) match either the regex or the list. For example
- debug:
msg: |
_srvcs:
{{ _srvcs|to_nice_yaml|indent(2) }}
when: debug|d(false)|bool
vars:
my_services:
- smartmontools.service
- smart-8.1
- smart-devel.0.0.1
_srvcs: "{{ my_services|intersect(services) }}"
gives
msg: |-
_srvcs:
- smartmontools.service
To enable the task run the playbook with the option -e debug=true.