replace-all-env-vars bash function

00-README.md

Usage

cat /file | replace-all-env-vars > /file
# Or:
replace-all-env-vars /file > /file

function replace-all-env-vars () {
  # Work with either `cat /file | replace-all-env-vars` and
  # `replace-all-env-vars /file`
  [ $# -ge 1 -a -f "$1" ] && input="$1" || input="-"
  local contents=$(cat $input)

  # Loop through each environment variable name
  for v in $(env | cut -d '=' -f1); do
    # Only look for things like `__ENV_PATH__`
    local needle="__ENV_${v}__"
    if [[ "${contents}" =~ "${needle}" ]]; then
      # Replace all instances of needle with the value of `$v`
      contents="${contents//$needle/${!v}}"
    fi
  done

  echo "${contents}"
}