ansible: how to check shell output

Question

I am new to Ansible(1.9.2). I want to check the current zlib version. If it is not 1.2.8 then Ansible need to install it from source.

The command which check the current zlib version is

root@node2 zlib-1.2.8]# cat /usr/local/include/zlib.h | grep "#define ZLIB_VERSION" | awk '{print $3}'
"1.2.8

My Ansible code

 - name: "Check zlib version "
      shell: "cat /usr/local/include/zlib.h | grep \"#define ZLIB_VERSION\" | awk '{print $3}'"
      register: zlib_version
    - name: "Debug result"
      debug: result
    - name: "Build zlib "
      command: "{{ item }} chdir=/home/zlib-1.2.8"
      with_items:
        - "./configure --prefix=/usr/local --shared"
        - make
        - make install
      when: "zlib_version!=1.2.8"

The debug prints "hello world"!!!

TASK: [Debug result] ********************************************************** 
ok: [192.168.111.81] => {
    "msg": "Hello world!"
}

How do I check the shell output and run command accordingly.

I have changed debug: var=zlib_version.stdout. It prints

TASK: [Debug result] ********************************************************** 
ok: [192.168.111.81] => {
    "var": {
        "zlib_version.stdout": "\"1.2.8\""
    }
}

However, now I need to write zlib_version.stdout.find ("\"1.2.8\"") == -1, twice. Is there an easy way so that Ansible skip all command,shell and unarchive when it matches zlib_version.stdout.find ("\"1.2.8\"") == -1?

 - name: "Check zlib version "
      shell: "cat /usr/local/include/zlib.h | grep \"#define ZLIB_VERSION\" | awk '{print $3}'"
      ignore_errors: true
      register: zlib_version
    - unarchive: src=/home/files/nigex/zlib-1.2.8.tar.gz   dest=/home/
      when: zlib_version.stdout.find ("\"1.2.8\"") == -1

    - name: "Debug result"
      debug: var=zlib_version.stdout
    - name: "Build zlib "
      command: "{{ item }} chdir=/home/zlib-1.2.8"
      with_items:
        - "./configure --prefix=/usr/local --shared"
        - make
        - make install
      when: zlib_version.stdout.find ("\"1.2.8\"") == -1

Answer 1

The output of shell command is available through stdout property. So zlib_version.stdout will give you the output of the command.

- name: "Debug result"
  debug: var=zlib_version.stdout

A simple role can be created to avoid writing the condition twice. Something like this:

# file roles/zlib/tasks/main.yml
---
- unarchive: src=/home/files/nigex/zlib-1.2.8.tar.gz   dest=/home/

- name: "Build zlib "
  command: "{{ item }} chdir=/home/zlib-1.2.8"
  with_items:
    - "./configure --prefix=/usr/local --shared"
    - make
    - make install

Then include the role only when the condition is true.

# pre_tasks is needed instead of tasks since this needs to be run before the role is included

pre_tasks:
  - name: "Check zlib version "
    shell: "cat /usr/local/include/zlib.h | grep \"#define ZLIB_VERSION\" | awk '{print $3}'"
    ignore_errors: true
    register: zlib_version

roles:
  - { role: zlib, when: "zlib_version.stdout.find ('\"1.2.8\"') == -1" }