Remove only trailling whitespaces from stdout_lines - ansible

Question

I need to assert the policy-maps from Cisco devices. And Cisco for some reason adds trailing whitespaces on some lines, but not all. I want to remove them, but, only the trailing whitespaces.
- name: Get running class-map & policy-map config
vars:
ansible_connection: network_cli
ios_command:
commands:
- 'show run | sec class-map|policy-map'
register: show_policy
- name: Print trim
debug:
var: show_policy.stdout_lines | trim
- name: Ansible block with assert module
block:
- name: Validate running line
ansible.builtin.assert:
that:
- "lookup('template', 'policy_desired.j2').splitlines() in show_policy.stdout_lines"
success_msg: "TEST: {{ UNIT_HOSTNAME }}: VALIDATE RUNNING POLICY: PASSED"
fail_msg: "TEST: {{ UNIT_HOSTNAME }}: VALIDATE RUNNING POLICY: FAILED"
This gives the following output:
{
"show_policy.stdout_lines | trim": [
[
"class-map match-any CM-QOS-GENERIC-BESTEFFORT-MARK",
" description Generic - Best Effort",
" match access-group name ACL-QOS-GENERIC-BESTEFFORT",
"class-map match-any CM-QOS-1P3Q-Q1",
" match dscp cs4 cs5 ef ", <--- Notice the whitespace
"class-map match-any CM-QOS-1P3Q-Q2",
" match dscp cs6 cs7 ",
"class-map match-any CM-QOS-1P3Q-Q3",
" match dscp cs1 "
]
]
}
The filter should then be added in the assert module so that it is gone when being asserted.
I have tried multiple things, but nothing seems to do the trick:
- name: Print trim
debug:
var: show_policy.stdout_lines | trim
- name: Print trim
debug:
var: show_policy.stdout_lines | strip
- name: Print trim
debug:
var: show_policy.stdout_lines.strip()
- name: Print trim
debug:
var: "{{ show_policy.stdout_lines | map('trim') }}"
- name: Print trim
debug:
var: "{{ show_policy.stdout_lines | trim }}"

Answer 1

You can use a regex_replace filter in order to achieve that.
Note: It seems, from you debug of show_policy.stdout_lines that it is actually a list of list, so you need the trim to happen on show_policy.stdout_lines.0.
Mind that, in the example below, I am purposely using a YAML multiline syntax, to save me from escaping the backslashes.
If you don't want to use this syntax, you will have to escaping those backslashes by doubling them (i.e. \\1 and \\s instead of \1 and \s).
- debug:
msg: >-
{{
show_policy.stdout_lines.0 | map('regex_replace', '(.*)\s+$', '\1')
}}
Given the task:
- debug:
msg: >-
{{
show_policy.stdout_lines | map('regex_replace', '(.*)\s+$', '\1')
}}
vars:
show_policy:
stdout_lines:
-
- "class-map match-any CM-QOS-GENERIC-BESTEFFORT-MARK"
- " description Generic - Best Effort"
- " match access-group name ACL-QOS-GENERIC-BESTEFFORT"
- "class-map match-any CM-QOS-1P3Q-Q1"
- " match dscp cs4 cs5 ef "
- "class-map match-any CM-QOS-1P3Q-Q2"
- " match dscp cs6 cs7 "
- "class-map match-any CM-QOS-1P3Q-Q3"
- " match dscp cs1 "
This yields:
msg:
- class-map match-any CM-QOS-GENERIC-BESTEFFORT-MARK
- ' description Generic - Best Effort'
- ' match access-group name ACL-QOS-GENERIC-BESTEFFORT'
- class-map match-any CM-QOS-1P3Q-Q1
- ' match dscp cs4 cs5 ef'
- class-map match-any CM-QOS-1P3Q-Q2
- ' match dscp cs6 cs7'
- class-map match-any CM-QOS-1P3Q-Q3
- ' match dscp cs1'

Answer 2

Since you've tried already to use the Python method .strip(), a minimal example playbook
---
- hosts: localhost
become: false
gather_facts: false
vars:
pol:
stdout_lines:
- "First line"
- " Second line with leading whitespace"
- "Third line with trailing whitespace "
- " Forth line with leading and trailing whitespaces "
- "Last line"
tasks:
- name: Print stripped
debug:
msg: "\"{{ item.rstrip() }}\""
loop: "{{ pol.stdout_lines }}"
will result into the output of
TASK [Print stripped] ***********************************************************
ok: [localhost] => (item=First line) =>
msg: '"First line"'
ok: [localhost] => (item= Second line with leading whitespace) =>
msg: '" Second line with leading whitespace"'
ok: [localhost] => (item=Third line with trailing whitespace ) =>
msg: '"Third line with trailing whitespace"'
ok: [localhost] => (item= Forth line with leading and trailing whitespaces ) =>
msg: '" Forth line with leading and trailing whitespaces"'
ok: [localhost] => (item=Last line) =>
msg: '"Last line"'
You may also have a look into .lstrip().
Unfortunately there is no direct Jinja2 Builtin Filter for, so a simple approach like
- name: Print trimmed
debug:
msg: "{{ pol.stdout_lines | map('trim') }}"
won't work since it
Strip leading and trailing characters, by default whitespace.
Further Q&A
How do I trim whitespace from a string?
How to proceed further?
If there are several use cases where one could take advantages from a filter like strip(), lstrip() and rstrip() it might be feasible to write an own filter plugin.
cat plugins/filter/rstrip.py
#!/usr/bin/python
class FilterModule(object):
def filters(self):
return {
'rstrip': self.rstrip,
}
def rstrip(self, String):
return String.rstrip()
which can then be used as follow
- name: Print stripped
debug:
msg: "{{ pol.stdout_lines | map('rstrip') }}"
and producing the required output.
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