A an example Ansible module written in bash

add-line.sh

#!/bin/bash

### DOCUMENTATION
#######
## This is a simple module that simply appends a provided line to the specified file
## It is intended to give sufficient content in order for anyone to develop Ansible modules in bash
#######
# ARGS #
## line
## path
## create
#
###

function validate_path {
  # $1 => the path to check for
  # $2 => boolean, whether to create the file or not if it's absent
  if [[ -d $1 ]]; then
    err "Path must be a file not a directory"
  elif [[ -f $1 ]]; then
    return 0
  elif ! [[ -f $1 ]] && [[ $2 == true ]]; then
    touch $1
  elif ! [[ -f $1 ]] && [[ $2 == false ]]; then
    err "Path '$1' does not exist and 'create' was set to false"
  fi
}

function err {
  # $1 => the string message to error out with
  printf '{"changed": "false", "failed": true, "msg": "%s"}' "$1"
  exit 1
}

function required {
  # $1 => the expanded value of the module param
  # $2 => the label of the module param
  if ! [[ -n "$1" ]]; then
    err "'$2' is required"
  fi
}

function set_default {
  # $1 => the expanded value of the module param
  # $2 => the label of the module param
  if ! [[ -n "$1" ]]; then
    echo $2
  else
    echo $1
  fi
}

function main {
  source $1
  # These values are defined from the source command above this line
  # $line
  # $path
  # $create
  required "${line}" line
  required "${path}" path
  create=$(set_default "${create}" false)

  validate_path ${path} ${create}
  echo ${line} >> ${path}

  printf '{"changed": "false", "path": "%s", "line": "%s"}' $path $line
}

main $1