Ansible regexp that will change only found string instead of whole line - regex

Question

I'm trying to setup playbook that will setup some docker services. I'm trying to pass some variables that are obtained by vars_prompt to docker-compose file.
replace:
path: files/docker-compose.yaml
regexp: 'SERVER_IP'
replace: '{{ ip_address }}'
Destination file
environment:
(...)
SERVER_IP: 'SERVICE_IP_ADDR'
(...)
Right now such task replace whole line with ip_address variable
expected result
environment:
(...)
SERVER_IP: ip_address
(...)

Answer 1

Instead of the modules replace or lineinfile, a more robust solution would be updating the dictionary. For example, given the file
shell> cat files/docker-compose.yaml
environment:
k1: v1
SERVER_IP: 'SERVICE_IP_ADDR'
k3: v3
and the below variables
dc_file: "{{ playbook_dir }}/files/docker-compose.yaml"
ip_address: 10.1.0.10
declare the dictionary dc_update
dc_update:
environment:
SERVER_IP: '{{ ip_address }}'
Include the content of the file into the dictionary dc
- include_vars:
file: "{{ dc_file }}"
name: dc
and declare the below variable
docker_compose: "{{ dc|combine(dc_update, recursive=true) }}"
This gives the updated configuration
docker_compose:
environment:
SERVER_IP: 10.1.0.10
k1: v1
k3: v3
Writes the updated configuration into the file
- copy:
dest: "{{ dc_file }}"
content: |
{{ docker_compose|to_nice_yaml(indent=2) }}
Running the play with the --diff options gives
TASK [copy] *******************************************************************
--- before: /export/scratch/tmp7/test-176/files/docker-compose.yaml
+++ after: /home/admin/.ansible/tmp/ansible-local-667065tpus_pfk/tmpnkohmmiz
## -1,4 +1,4 ##
environment:
+ SERVER_IP: 10.1.0.10
k1: v1
- SERVER_IP: 'SERVICE_IP_ADDR'
k3: v3
changed: [localhost]
shell> cat files/docker-compose.yaml
environment:
SERVER_IP: 10.1.0.10
k1: v1
k3: v3
Notes:
Example of a complete playbook for testing
- hosts: localhost
vars:
dc_file: "{{ playbook_dir }}/files/docker-compose.yaml"
ip_address: 10.1.0.10
dc_update:
environment:
SERVER_IP: '{{ ip_address }}'
docker_compose: "{{ dc|combine(dc_update, recursive=true) }}"
tasks:
- include_vars:
file: "{{ dc_file }}"
name: dc
- debug:
var: docker_compose
- copy:
dest: "{{ dc_file }}"
content: |
{{ docker_compose|to_nice_yaml(indent=2) }}
You can use modules replace and lineinfile. See the examples below on how to get the expected result by matching the key SERVER_IP, the value SERVICE_IP_ADDR, or both. All options below give the same result
--- before: /export/scratch/tmp7/test-176/files/docker-compose.yaml (content)
+++ after: /export/scratch/tmp7/test-176/files/docker-compose.yaml (content)
## -1,4 +1,4 ##
environment:
k1: v1
- SERVER_IP: 'SERVICE_IP_ADDR'
+ SERVER_IP: '10.1.0.10'
k3: v3
changed: [localhost]
- hosts: localhost
vars:
dc_file: "{{ playbook_dir }}/files/docker-compose.yaml"
ip_address: 10.1.0.10
tasks:
- replace:
path: "{{ dc_file }}"
regexp: SERVICE_IP_ADDR
replace: "{{ ip_address }}"
when: replace_by_value|d(false)|bool
- replace:
path: "{{ dc_file }}"
regexp: "SERVER_IP:.*"
replace: "SERVER_IP: '{{ ip_address }}'"
when: replace_by_key|d(false)|bool
- replace:
path: "{{ dc_file }}"
regexp: "SERVER_IP: \\'SERVICE_IP_ADDR\\'"
replace: "SERVER_IP: '{{ ip_address }}'"
when: replace_by_kv|d(false)|bool
- lineinfile:
backrefs: true
path: "{{ dc_file }}"
regexp: "^(.*)\\'SERVICE_IP_ADDR\\'$"
line: "\\1'{{ ip_address }}'"
when: lineinfile_by_value|d(false)|bool
- lineinfile:
backrefs: true
path: "{{ dc_file }}"
regexp: "^(\\s*)SERVER_IP:.*$"
line: "\\1SERVER_IP: '{{ ip_address }}'"
when: lineinfile_by_key|d(false)|bool
- lineinfile:
backrefs: true
path: "{{ dc_file }}"
regexp: "^(\\s*)SERVER_IP: \\'SERVICE_IP_ADDR\\'$"
line: "\\1SERVER_IP: '{{ ip_address }}'"
when: lineinfile_by_kv|d(false)|bool

Answer 2

After some test I've found solution for that.
replace:
path: files/docker-compose.yaml
regexp: (\s+)\'SERVICE_IP_ADDR\'(\s+.*)?$
replace: \1'{{ ip_address }}'\2