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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?
437
There is no Ansible grep module, but you can use the grep commands along with shell module or command module. We can store the results of the task and use it in various conditional statements, print them or use them for debugging purposes.
Non-zero return codes are normally used for failure cases with a 0 return code used for a successful command so this can give the impression the command has failed when it has not.
The shell module executes commands in nodes or Shell scripts. Another dedicated Ansible module is Script that transfers the Shell script from the control machine to the remote server and executes it. In the command module, the given command executes on all selected nodes.
The shell module takes the command name followed by a list of space-delimited arguments. It is almost exactly like the command module but runs the command through a shell ( /bin/sh ) on the remote node. For Windows targets, use the win_shell module instead.
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.
193
Like you observed, ansible will stop execution if the grep exit code is not zero. You can ignore it with ignore_errors.
Another trick is to pipe the grep output to cat. So cat exit code will always be zero since its stdin is grep's stdout. It works if there is a match and also when there is no match. Try it.
- name: Get the http_status shell: grep "http_status=" /var/httpd.txt | cat register: cmdln check_mode: no If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
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