edit string in a multi-line file

[Kathy L]

I am trying to edit a string in a multi-line file.  For instance, if I had this string:

This is a file and I am editing it

I want to add the string "new" in front of file if it does not exist already.

I've tried lineinfile, but the issue is that I don't know what else is on the line.  There could be more data after "This is a file and I am editing it" that I don't want to change.  What is the best way to do this?

[dulh...@mailbox.org]

would this do what you want?

 

 

    - name: edit a line in a file
      ansible.builtin.command:
        chdir: /home/username/
        cmd: 'sed -i "s/This is a file/This is a new file/" somefile'

 

 

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[dulh...@mailbox.org]

 

curious actually how this can be achieved with sophisticated regex and the lineinfile module

 

 

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[Kathy Lyons]

That will work - yes.  I was so focused on using lineinfile or another ansible module, I forgot about sed.  Thank you!

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[Hearn, Stan J.]

What you want to use is backrefs.

 

https://docs.ansible.com/ansible/latest/collections/ansible/builtin/lineinfile_module.html

 

An Example from the document:

# NOTE: Yaml requires escaping backslashes in double quotes but not in single quotes

- name: Ensure the JBoss memory settings are exactly as needed

  ansible.builtin.lineinfile:

    path: /opt/jboss-as/bin/standalone.conf

    regexp: '^(.*)Xms(\d+)m(.*)$'

    line: '\1Xms${xms}m\3'

    backrefs: yes

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[Todd Lewis]

Here's one solution. It uses backrefs and a negative lookahead assertion.

- name: Test lineinfile
  hosts: localhost
  gather_facts: false
  tasks:
    - name: Create a file to work on
      ansible.builtin.copy:
        content: |
           First line of a file
           Second line of the same file
           This is a file and I am editing it. Extra Stuff!
           Fourth line of this file
        dest: /tmp/textfile.txt

    - name: Show the file content
      ansible.builtin.debug:
        msg: "{{ lookup('file', '/tmp/textfile.txt') }}"

    - name: Insert "new" before "file" in the 3rd line
      ansible.builtin.lineinfile:
        path: /tmp/textfile.txt
        regexp: '(This is a )(?!>new)(file and I am editing it\..*)'
        backrefs: true
        line: '\1new \2'

    - name: Show the file content a 2nd time
      ansible.builtin.debug:
        msg: "{{ lookup('file', '/tmp/textfile.txt') }}"

    - name: Second identical lineinfile should not make changes
      ansible.builtin.lineinfile:
        path: /tmp/textfile.txt
        regexp: '(This is a )(?!>new)(file and I am editing it\..*)'
        backrefs: true
        line: '\1new \2'

    - name: Show the file content a 3nd time
      ansible.builtin.debug:
        msg: "{{ lookup('file', '/tmp/textfile.txt') }}"

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-- 
Todd