Ansible shell module returns error when grep results are empty

Question

I am using Ansible's shell module to find a particular string and store it in a variable. But if grep did not find anything I am getting an error.

Example:

- name: Get the http_status
  shell: grep "http_status=" /var/httpd.txt
  register: cmdln
  check_mode: no

When I run this Ansible playbook if http_status string is not there, playbook is stopped. I am not getting stderr.

How can I make Ansible run without interruption even if the string is not found?

Answer 1

grep by design returns code 1 if the given string was not found. Ansible by design stops execution if the return code is different from 0. Your system is working properly.

To prevent Ansible from stopping playbook execution on this error, you can:

• add ignore_errors: yes parameter to the task

• use failed_when: parameter with a proper condition

Because grep returns error code 2 for exceptions, the second method seems more appropriate, so:

- name: Get the http_status
  shell: grep "http_status=" /var/httpd.txt
  register: cmdln
  failed_when: "cmdln.rc == 2"
  check_mode: no

You might also consider adding changed_when: false so that the task won't be reported as "changed" every single time.

All options are described in the Error Handling In Playbooks document.