How to strip newline from shell command's standard output run via ansible

Question

So I have a scenario where I am executing a shell command on a machine using ansible to get some information on standard output . I am using register to log its result in a variable my_info and print my_info using debug , I am seeing its result with \n appended to it (Ansible has appended \n .Same command on linux do not appends \n" ).When I use the my_info in templates for a config it prints a new line in config hence messing up my config .

Here is how the code and output goes .

Ansible code :

- name: calculate range address start
  raw:  grep 'CONFIG_PARAMS' /path/to/the/file | head -n 1
  register: my_info

Output :

ok: [My_HOST] => {
    "msg": "CONFIG_PARAMS\n"
}

How can we strip the space from this output or possibly make a change in template so that new line don't gets printed .

Solution 1

In the documentation of raw_module, it asks to use it only in specific cases:

Executes a low-down and dirty SSH command, not going through the module subsystem. This is useful and should only be done in two cases. The first case is installing python-simplejson on older (Python 2.4 and before) hosts that need it as a dependency to run modules, since nearly all core modules require it. Another is speaking to any devices such as routers that do not have any Python installed. In any other case, using the shell or command module is much more appropriate. Arguments given to raw are run directly through the configured remote shell.

So, I tested simple echo calls with raw and shell modules:

- name: System setup
  hosts: 127.0.0.1
  connection: local

  tasks:
    - name: simple print hello
      raw:  echo 'hello'
      register: my_info

    - debug:
        msg: '{{ my_info.stdout }}'

and it outputs with a new line:

TASK: [debug ]    **************************************************************** 
ok: [127.0.0.1] => {
    "msg": "hello\n"
}

and by using the shell module:

- name: System setup
  hosts: 127.0.0.1
  connection: local

  tasks:
    - name: simple print hello
      action:  shell echo 'hello'
      register: my_info

    - debug:
        msg: '{{ my_info.stdout }}'

and this results in:

TASK: [debug ]    **************************************************************** 
ok: [127.0.0.1] => {
    "msg": "hello"
}

And, you can see the difference in the output.

Solution 2

You can use the built-in filters of Jinja2 to achieve this. Specifically, use trim, e.g.:

- debug: msg='{{ my_info.stdout | trim}}'

Solution 3

You could remove the newline from stdout, using

grep 'CONFIG_PARAMS' /path/to/the/file | head -n 1 | tr -d '\n'

If you run this on a command-line you'll see something like

me@machine:~ > echo cat | tr -d '\n'
catme@machine:~ >

because linux is adding the newline.