Ansible alternatives for shell tricks

Ansible alternatives for shell tricks

If you’re used to shells and their commands like bash, sed and grep, here are a few alternatives for Ansible.

Using these native alternatives has an advantage, developers maintain the Ansible modules for you, they are idempotent and likely work on more distributions or platforms.

Grep

Imagine you need to know if a certain patter is in a file. With a shell script you would use something like this:

grep "pattern" file.txt && do-something-if-pattern-is-found.sh

With Ansible you can achieve a similar result like this:

--- 
- hosts: all
  gather_facts: no

  tasks:
    - name: check if pattern if found
      lineinfile:
        path: file.txt
        regexp: '.*pattern.*'
        line: 'whatever'
      register: check_if_pattern_is_found
      check_mode: yes
      notify: do something

  handlers:
    - name: do something
      command: do-something-if-pattern-is-found.sh

Hm, much longer than the bash example, but native Ansible!

Sed

So you like sed? So do I. It’s one of the most powerful tools I’ve used.

Lets replace some pattern in a file:

sed 's/pattern_a/pattern_b/g' file.txt

This would repace all occurences of pattern_a for pattern_b. Lets see what Ansible looks like.

---
- name: replace something
  gather_facts: no

  tasks:
    - name: replace patterns
      lineinfile:
        path: file.txt
        regexp: '^(.*)pattern_a(.*)$'
        line: '\1pattern_b\2'

Have a look at the lineinfile module documentation for more details.

Find and remove.

The find (UNIX) tools is really powerful too, imagine this command:

find / -name some_file.txt -exec rm {} \;

That command would find all files (and directories) named some_file.txt and remove them. A bit dangerous, but powerful.

With Ansible:

- name: find and remove
  gather_facts: no

  tasks:
    - name: find files
      find:
        paths: /
        patterns: some_file.txt
      register: found_files

    - name: remove files
      file:
        path: "{{ item.path }}"
        state: absent
      loop: "{{ found_files.results }}"

Conclusion

Well, have fun with all non-shell solutions. You hardly needs the shell or command modules when you get the hang of it.