Based on this example:

- lineinfile: dest=/opt/jboss-as/bin/standalone.conf regexp='^(.*)Xms(\d+)m(.*)$' line='\1Xms${xms}m\3' backrefs=yes

from this documentation, it was tried to do a regex-replace in Ansible.

Ansible version

user@server:/home$ ansible --version



Ansible snippets:

- lineinfile:
  dest: /path/to/file

attempt 2

- lineinfile:
  dest: /path/to/file

Expected outcome:


Current outcome:



  1. Why is the outcome \1030 instead of hello030?
  2. How to solve it?
  • what version of ansible are you running? – Petter H Sep 15 '16 at 11:05
  • @PetterH ansible – 030 Sep 15 '16 at 11:08
  • The default is backrefs: no, your snips don't define it. Can you test with backrefs: yes? I don't have access just now to do so. – jscott Sep 16 '16 at 1:25

Why is the outcome \1030 instead of hello030?

The lineinfile module default is backrefs: false. Your regexp='^(hello)world$' matches the entire contents of file. Literal from line='\1030' replaces contents.

How to solve it?

  1. Turn on backrefs with backrefs: true
  2. Use a named group in line:

A backref followed by numbers will not function as expected. You will need a named group instead. e.g. \g<1>

- name: Replace the world
    dest: file
    regexp: '^(hello)world$'
    line: '\g<1>030'
    backrefs: true

I suppose it is because it matches whole \1030 (as 1030-th backref). Maybe try \1 030 first and you will see, if it is the reason.

  • line='\1Xms${xms}m\3' returns \1Xms as well – 030 Sep 15 '16 at 23:13

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