https://stackoverflow.com/a/77622481/9401096

session.txt

$ ansible --version
ansible [core 2.16.1]
  config file = None
  configured module search path = ['/home/user/.ansible/plugins/modules', '/usr/share/ansible/plugins/modules']
  ansible python module location = /home/user/.local/lib/python3.10/site-packages/ansible
  ansible collection location = /home/user/.ansible/collections:/usr/share/ansible/collections
  executable location = /home/user/.local/bin/ansible
  python version = 3.10.12 (main, Nov 20 2023, 15:14:05) [GCC 11.4.0] (/usr/bin/python3)
  jinja version = 3.1.2
  libyaml = True

$ tree
.
├── run_ansible.sh
├── test_encryption.sh
├── test_playbook.yml
└── test_var.yml

0 directories, 4 files

$ cat test_var.yml 
test_var: toto

$ # I will use toto as password

$ ansible-vault encrypt test_var.yml 
New Vault password: 
Confirm New Vault password: 
Encryption successful

$ # We can check the file is correctly encrypted

$ cat test_var.yml 
$ANSIBLE_VAULT;1.1;AES256
61393565363161666536326162346135613736623238393839636533336666333331343339646239
3838333136343936613430373765383664383364333163620a383636343736373638396439306331
36636562383561653737366661336364653037613938366164386364383134636238336431663261
3466363236336564660a363935303863333734353863313031666334346338373034333561653731
3939

$ # As a first test of the solution let's check the content of the encrypted file using a script

$ cat test_encryption.sh 
#!/bin/bash
read -p "Please enter the Ansible Vault password ? : " vault_password

echo ${vault_password,,} | ansible-vault view test_var.yml --vault-password-file=/bin/cat

$ ./test_encryption.sh 
Please enter the Ansible Vault password ? : toto
test_var: toto

$ # And without surprise, we can use that file in a playbook we call from the same kind of script

$ cat test_playbook.yml 
---
- hosts: localhost
  gather_facts: false

  vars_files:
    - test_var.yml

  tasks:
    - debug:
        var: test_var

$ cat run_ansible.sh 
#!/bin/bash
read -p "Please enter the Ansible Vault password ? : " vault_password

echo ${vault_password,,} | ansible-playbook test_playbook.yml --vault-password-file=/bin/cat

$ ./run_ansible.sh 
Please enter the Ansible Vault password ? : toto

PLAY [localhost] **************************************************************************************************************************************************************************************************

TASK [debug] ******************************************************************************************************************************************************************************************************
ok: [localhost] => {
    "test_var": "toto"
}

PLAY RECAP ********************************************************************************************************************************************************************************************************
localhost                  : ok=1    changed=0    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0