output

$ ./test.sh 7.6
 [WARNING]: Unable to parse /home/akrzos/code/openshift-scale/hosts as an inventory source

 [WARNING]: No inventory was parsed, only implicit localhost is available

ERROR! Syntax Error while loading YAML.
  did not find expected ',' or '}'

The error appears to be in '<string>': line 1, column 32, but may
be elsewhere in the file depending on the exact syntax problem.

play.yaml

---

- hosts: localhost
  connection: local

  # Set global vars
  vars:
    BUILD_DIR: '{{ build_dir | default("${HOME}/build") }}'
    INSTALL_DIR: '{{ install_dir | default("${HOME}/custom_fftw") }}'
    RHEL_VERSION: '{{ rhel_version | default("7") }}'
  tasks:
    - debug: msg="{{BUILD_DIR}}"
    - debug: msg="{{INSTALL_DIR}}"
    - debug: msg="{{RHEL_VERSION}}"

test.sh

#!/bin/bash


RHEL_VERSION=$1
FFTW_INSTALL_DIR=${HOME}/cust{om_fftw
FFTW_BUILD_DIR=${HOME}/build
ansible-playbook -i hosts play.yaml --extra-vars="{install_dir: ${FFTW_INSTALL_DIR}, build_dir: ${FFTW_BUILD_DIR}, rhel_version: ${RHEL_VERSION}}"