regex_replace('^p(\d+).*$', '\\1')
'\\1' in the second argument is a "backref" (backwards reference) to the (\d+)
in the first argument. It seems it is looking for an expression with digits and
extracting the digits.
Your list 't' has names with p1_xyz, p2_xyz, p4_xyx so this regex would extract
the 1, 2, 4 digits from those strings.
Your string 's' has digits 1 and 2. You are getting two lines of output as
expected.
Walter
--
Walter Rowe, Division Chief
Infrastructure Services Division
Mobile: 202.355.4123
On Jan 8, 2024, at 4:15 PM, [email protected] <[email protected]> wrote:
Hi - Does anyone (who understands how backslashes work in Ansible/YAML) know
why both of the following tasks work:
(ansible2_15_8) rowagn@localhost:~#> cat d.yml
- hosts: all
gather_facts: no
vars:
s: 'This is a string containing 1 and 2.'
t:
- p1_xyz
- p2_xyz
- p4_xyz
tasks:
- name: single backslash
debug:
msg: '{{ item }} is in s'
loop: '{{ t }}'
when: ( item | regex_replace('^p(\d+).*$', '\\1') ) in s
- name: double backslash
debug:
msg: '{{ item }} is in s'
loop: '{{ t }}'
when: ( item | regex_replace('^p(\\d+).*$', '\\1') ) in s
(ansible2_15_8) rowagn@localhost:~#> ansible-playbook -i l d.yml
PLAY [all]
******************************************************************************************************************************************************
TASK [single backslash]
*****************************************************************************************************************************************
ok: [localhost] => (item=p1_xyz) => {
"msg": "p1_xyz is in s"
}
ok: [localhost] => (item=p2_xyz) => {
"msg": "p2_xyz is in s"
}
skipping: [localhost] => (item=p4_xyz)
TASK [double backslash]
*****************************************************************************************************************************************
ok: [localhost] => (item=p1_xyz) => {
"msg": "p1_xyz is in s"
}
ok: [localhost] => (item=p2_xyz) => {
"msg": "p2_xyz is in s"
}
skipping: [localhost] => (item=p4_xyz)
PLAY RECAP
******************************************************************************************************************************************************
localhost : ok=2 changed=0 unreachable=0 failed=0
skipped=0 rescued=0 ignored=0
The tasks are extracting the number from the strings in list t and then looking
for that number in string s. What is strange is the second example at
https://docs.ansible.com/ansible/latest/collections/ansible/builtin/regex_replace_filter.html#examples
indicates the backslashes in both parameters need to be doubled, but the above
testing shows double backslashes are not required in the first parameter (they
are required in the second parameter).
Thanks
Rob
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