Simple shell script that generate env vars from files

dotenv.sh

#!/bin/bash
#
# Read one or more dotfiles, and load
#
# Author: mrjk


set -euo pipefail

_log ()
{
  #return 0
  >&2 echo "$@"
}

fn_update ()
{
  local kind=$1
  shift 1
  
  case "$kind" in
    env)
      local name=$1
      shift 1
      _log "INFO: Update from env: $name"
      STORED_VARS_ENV["$name"]="$@"
      ;;
    file)
      local file=$1
      local name=$2
      shift 2
      
      if $DOTENV_FIRST_ONLY; then
        # Ensure destination vars does not exists
        if [[ -v STORED_VARS_FILES["$name"] ]]; then
          _log "INFO: Skip already defined var '$name' from $file"
          return 0
        fi
      fi

      _log "INFO: Update from file '$file': $name"
      STORED_VARS_FILES["$name"]="$@"
      ;;
    *)
      echo "Unsupported: $kind"
      return 1
    ;;
  esac

}

get_var_names ()
{
  local file=$1
  sed -En  '/^[a-zA-Z0-9_]+=.*/s/([^=]*)=.*/\1/p' "$file"
}

show_env_vars ()
{

  local prefix="env_"
  for vname in ${VAR_NAMES[@]}; do

    # Skip if known vars is not declared
    [[ -v "$vname" ]] || continue

    # Display loading function
    local value=${!vname}
    echo "fn_update env '$vname' \"$value\""
  done

}

show_file_vars ()
{
  local file=$1
  local prefix=${2:-local_}

  (
    # Clear environment
    unset ${VAR_NAMES[@]}

    # Parse file without bash
    eval "$(cat $file)"

    for vname in ${VAR_NAMES[@]}; do

      # Skip if known vars is not declared
      if ! [[ -v "$vname" ]]; then
        #_log INFO "Skip missing var: $vname in $file"
        continue
      else
        _log DEBUG "Found var '$vname' in $file"
      fi

      # Display loading function
      local value="${!vname}"
      echo "fn_update file '$file' '$vname' \"$value\""

      #if [[ -n "${value}" ]]; then

      #  #echo "${prefix}$vname=\"$value\""
      #  #echo "STORED_VARS['$vname']=\"$value\""

      #  #STORED_VARS["$vname"]="$value"
      #fi
    done
  )

}

show_vals ()
{
  local files=${@:-$DOTENV_ENV_FILES}

  # Check missing files
  local _files=
  for file in $files; do
    if [[ -f "$file" ]] ; then
      _files="${_files} $file"
    else
      if ! $DOTENV_IGNORE_MISSING_FILES; then
        >&2 echo  "ERROR: Missing file: $file"
        return 1
      else
        _log DEBUG "Ignore missing file: $file"
        continue
      fi
    fi
  done
  files=$_files

  # Build known vars list
  local VAR_NAMES=()
  for file in $files; do

    for name in $(get_var_names "$file"); do
      VAR_NAMES+=( "$name" )
    done
  done

  _log "INFO: Var names: ${VAR_NAMES[@]}"
  declare -A STORED_VARS_ENV=()
  declare -A STORED_VARS_FILES=()

  # Parse each files
  arrays_code=$(
    for file in $files; do
      echo "# Parse file: $file"
      show_file_vars $file local_
    done
    show_env_vars
  )

  # Process var definitions
  eval "$arrays_code"


  # Process var merging
  declare -A FINAL_ENV=()

  # Insert file variables
  for name in "${!STORED_VARS_FILES[@]}"; do
    #_log "INFO: var: ${name}: ${STORED_VARS_FILES[$name]}"
    FINAL_ENV["$name"]=${STORED_VARS_FILES[$name]}
  done

  # Override environment vars
  if $DOTENV_ENV_OVERRIDE; then
    for name in "${!STORED_VARS_ENV[@]}"; do
      #_log "INFO: env: ${name}: ${STORED_VARS_ENV[$name]}"
      FINAL_ENV["$name"]=${STORED_VARS_ENV[$name]}
    done
  fi

  # Generate output
  >&2 echo 'INFO: Generated bash code:'
  local prefix=''
  local snames="${!FINAL_ENV[@]}"
  if $DOTENV_SORTED; then
    # Sort vars by name
    snames=$( tr ' ' '\n' <<< "$snames" | sort )
  fi
  if $DOTENV_EXPORT; then
    prefix="export "
  fi

  for name in $snames ; do
    echo "${prefix}${name}=\"${FINAL_ENV[$name]}\""
  done
}

show_usage ()
{
  cat <<EOF
Simple tool to fetch environment variables from files

Usage:
  $0 [show|run]

EOF
}

main ()
{
  local cmd=$1
  shift 1

  # Set to true to enable alphabetical sort
  DOTENV_SORTED=${DOTENV_SORTED:-true}

  # Set to true to prefix output with export. Useful for sourcing shell output
  DOTENV_EXPORT=${DOTENV_EXPORT:-false}

  # Default env files to load. Missing files are ignored silentely
  DOTENV_ENV_FILES=${DOTENV_ENV_FILES:-.env .env.secrets .env.local}

  # Ignore missing files
  DOTENV_IGNORE_MISSING_FILES=${DOTENV_IGNORE_MISSING_FILES:-true}

  # Environment vars act as overrides
  DOTENV_ENV_OVERRIDE=${DOTENV_ENV_OVERRIDE:-true}

  # Set to true to only consider the first found variable
  DOTENV_FIRST_ONLY=${DOTENV_FIRST_ONLY:-false}

  # Process command
  case "$cmd" in
    show)
      show_vals $@
      ;;

    run)
      eval "$(DOTENV_EXPORT=true show_vals)"
      exec "$@"
      ;;

    help|--help|-h)
      show_usage
      ;;

    *)
      echo "Command not supported: $cmd"
      return 1
      ;;
  esac

}

main $@