local_action: shell error concatenate files - ansible

Question

There is such an error in my playbook. Why and how to fix it? (getting the list of updates of remote-hosts, concatenate lists into one file)
- name: Save update_deb_packs in file on ansible-host
copy:
content: "{{ update_deb_packs.stdout }}"
dest: ~/tmp/{{ inventory_hostname }}_update_deb_packs
delegate_to: 127.0.0.1
- name: merge files from different hosts in once
local_action: shell cat ~/tmp/* > ~/tmp/list_update
result:
TASK [Save update_deb_packs in file on ansible-host] *******************************************
changed: [g33-linux -> 127.0.0.1]
changed: [dell-e6410 -> 127.0.0.1]
TASK [merge files from different hosts in once] ********************************
changed: [g33-linux -> localhost]
fatal: [dell-e6410 -> localhost]: FAILED! => {"changed": true, "cmd": "cat ~/tmp/* > ~/tmp/list_update", "delta": "0:00:00.052968", "end": "2017-12-23 13:48:37.029706", "msg": "non-zero return code", "rc": 1, "start": "2017-12-23 13:48:36.976738", "stderr": "cat: /home/alex/tmp/list_update: input and output in one file", "stderr_lines": ["cat: /home/alex/tmp/list_update: input and output in one file"], "stdout": "", "stdout_lines": []}
to retry, use: --limit #/home/alex/.ansible/playbooks/update_deb_list.retry
directory ~/tmp is empty. After shell result file (list_update) file exists and true.

Answer 1

You use a glob ~/tmp/* and one of the files is ~/tmp/list_update, so effectively you order it to read and write to the same file with a redirection and system is refusing to do that.
You also didn't specify run_once, so the merge files from different hosts in once task will run as there are hosts defined for the play.
If you are sure ~/tmp/list_update didn't exist beforehand, adding run_once: true to that task would resolve the problem, but it's far from the best way.
Long story short, you can achieve what you want in one task, for example
with a Jinja2 template:
- copy:
content: "{% for host in ansible_play_hosts %}{{ hostvars[host].update_deb_packs.stdout }}\n{% endfor %}"
dest: ~/tmp/list_update
delegate_to: localhost
run_once: true
You can add separators with host-value to indicate what data is coming from which host:
content: "{% for host in ansible_play_hosts %}From host: {{ host }}\n{{ hostvars[host].update_deb_packs.stdout }}\n{% endfor %}"
using operations on lists:
content: "{{ ansible_play_hosts | map('extract', hostvars, 'update_deb_packs') | map(attribute='stdout') | list }}"