This assumes you have installed Ansible, are familiar with the ansible-playbook command and the shell command, and have created a playbook.

The register module can be used to store the standard output (stdout), standard error (stderr) and return code (rc) of a command. In this example, the stdout/stderr/rc of the ps command will be stored in a variable named "out". You can then do something with the register, such as printing the output and return code.

---
- hosts: all
  tasks:
    - name: list command
      shell: "ls /tmp"
      register: out

    - name: standard out
      debug: 
        msg: "{{ out.stdout_lines }}"

    - name: standard error
      debug: 
        msg: "{{ out.stderr_lines }}"

    - name: return code
      debug: 
        msg: "{{ out.rc }}"

Running this playbook should return the following. In this example, standard out returns a file or directory in the /tmp directory named "foo", there was no standard error, and the return code is 0 (success).

PLAY [all]

TASK [Gathering Facts]
ok: [server1.example.com]

TASK [list command]
ok: [server1.example.com]

TASK [standard out]
ok: [server1.example.com] => {
    "msg": "foo"
}

TASK [standard error]
ok: [server1.example.com] => {
    "msg": ""
}

TASK [return code]
ok: [server1.example.com] => {
    "msg": "0"
}

PLAY RECAP
server1.example.com : ok=1  changed=0  unreacable=0  failed=0