Script execution using ansible [duplicate] - amazon-web-services

Question

I am using Ansible to deploy my project and I trying to check if an specified package is installed, but I have a problem with it task, here is the task:
- name: Check if python-apt is installed
command: dpkg -l | grep python-apt
register: python_apt_installed
ignore_errors: True
And here is the problem:
$ ansible-playbook -i hosts idempotent.yml
PLAY [lxc-host] ***************************************************************
GATHERING FACTS ***************************************************************
ok: [10.0.3.240]
TASK: [idempotent | Check if python-apt is installed] *************************
failed: [10.0.3.240] => {"changed": true, "cmd": ["dpkg", "-l", "|", "grep", "python-apt"], "delta": "0:00:00.015524", "end": "2014-07-10 14:41:35.207971", "rc": 2, "start": "2014-07-10 14:41:35.192447"}
stderr: dpkg-query: error: package name in specifier '|' is illegal: must start with an alphanumeric character
...ignoring
PLAY RECAP ********************************************************************
10.0.3.240 : ok=2 changed=1 unreachable=0 failed=0
Why is illegal this character '|' .

Answer 1

From the doc:
command - Executes a command on a remote node
The command module takes the command name followed by a list of
space-delimited arguments. The given command will be executed on all
selected nodes. It will not be processed through the shell, so
variables like $HOME and operations like "<", ">", "|", and "&" will
not work (use the shell module if you need these features).
shell - Executes a commands in 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.
Therefore you have to use shell: dpkg -l | grep python-apt.

Answer 2

read about the command module in the Ansible documentation:
It will not be processed through the shell, so .. operations like "<", ">", "|", and "&" will not work
As it recommends, use the shell module:
- name: Check if python-apt is installed
shell: dpkg -l | grep python-apt
register: python_apt_installed
ignore_errors: True
For what it's worth, you can check/confirm the installation in a debian environment using the apt command:
- name: ensure python-apt is installed
apt: name=python-apt state=present