How to create an empty file with Ansible?

What is the easiest way to create an empty file using Ansible? I know I can save an empty file into the files directory and then copy it to the remote host, but I find that somewhat unsatisfactory.

Another way is to touch a file on the remote host:

- name: create fake 'nologin' shell
  file: path=/etc/nologin state=touch owner=root group=sys mode=0555

But then the file gets touched every time, showing up as a yellow line in the log, which is also unsatisfactory...

Is there any better solution to this simple problem?

The documentation of the file module says > If state=file, the file will NOT be created if it does not exist, see the copy or template module if you want that behavior.

So we use the copy module, using force=no to create a new empty file only when the file does not yet exist (if the file exists, its content is preserved).

- name: ensure file exists
  copy:
    content: ""
    dest: /etc/nologin
    force: no
    group: sys
    owner: root
    mode: 0555

This is a declarative and elegant solution.

Something like this (using the stat module first to gather data about it and then filtering using a conditional) should work:

- stat: path=/etc/nologin
  register: p

- name: create fake 'nologin' shell
  file: path=/etc/nologin state=touch owner=root group=sys mode=0555
  when: p.stat.exists is defined and not p.stat.exists

You might alternatively be able to leverage the changed_when functionality.

Another option, using the command module:

- name: Create file
  command: touch /path/to/file
  args:
    creates: /path/to/file

The 'creates' argument ensures that this action is not performed if the file exists.

file module provide way to touch file without modifying its time.

- name: Touch again the same file, but dont change times this makes the task idempotent
  file:
    path: /etc/foo.conf
    state: touch
    mode: u+rw,g-wx,o-rwx
    modification_time: preserve
    access_time: preserve

Reference: https://docs.ansible.com/ansible/latest/modules/file_module.html

Building on the accepted answer, if you want the file to be checked for permissions on every run, and these changed accordingly if the file exists, or just create the file if it doesn't exist, you can use the following:

- stat: path=/etc/nologin
  register: p

- name: create fake 'nologin' shell
  file: path=/etc/nologin 
        owner=root
        group=sys
        mode=0555
        state={{ "file" if  p.stat.exists else "touch"}}

file: path=/etc/nologin state=touch

Full equivalent of touch (new in 1.4+) - use stat if you don't want to change file timestamp.

Turns out I don't have enough reputation to put this as a comment, which would be a more appropriate place for this:

Re. AllBlackt's answer, if you prefer Ansible's multiline format you need to adjust the quoting for state (I spent a few minutes working this out, so hopefully this speeds someone else up),

- stat:
    path: "/etc/nologin"
  register: p

- name: create fake 'nologin' shell
  file:
    path: "/etc/nologin"
    owner: root
    group: sys
    mode: 0555
    state: '{{ "file" if  p.stat.exists else "touch" }}'

Changed if file not exists. Create empty file.

- name: create fake 'nologin' shell
  file:
    path: /etc/nologin
    state: touch
  register: p
  changed_when: p.diff.before.state == "absent"

A combination of two answers, with a twist. The code will be detected as changed, when the file is created or the permission updated.

- name: Touch again the same file, but dont change times this makes the task idempotent
  file:
    path: /etc/foo.conf
    state: touch
    mode: 0644
    modification_time: preserve
    access_time: preserve
  changed_when: >
    p.diff.before.state == "absent" or
    p.diff.before.mode|default("0644") != "0644"

and a version that also corrects the owner and group and detects it as changed when it does correct these:

- name: Touch again the same file, but dont change times this makes the task idempotent
  file:
    path: /etc/foo.conf
    state: touch
    state: touch
    mode: 0644
    owner: root
    group: root
    modification_time: preserve
    access_time: preserve
  register: p
  changed_when: >
    p.diff.before.state == "absent" or
    p.diff.before.mode|default("0644") != "0644" or
    p.diff.before.owner|default(0) != 0 or
    p.diff.before.group|default(0) != 0

In order to create a file in the remote machine with the ad-hoc command

ansible client -m file -a"dest=/tmp/file state=touch"

Please correct me if I am wrong