0_prepare.sh

#!/usr/bin/env bash

TMP_BASE_DIR="$( cd "$(dirname "$0")" >/dev/null 2>&1 ; pwd -P )"
ENV_FILE="$TMP_BASE_DIR/.env"

# remove any existing .env file
if [ -f "$ENV_FILE" ]; then
    echo "" > "$ENV_FILE"
fi

# create .env that contains all globally needed environment variables
build_environment=$'
BASE_DIR="$TMP_BASE_DIR"

ARTIFACTS_DIR="$BASE_DIR/artifacts"
CONFIG_DIR="$BASE_DIR/config"
PATCH_DIR="$BASE_DIR/patches"
OUT_DIR="$BASE_DIR/out"

UBOOT_VER="2019-01-bpi-r2"
UBOOT_DIR="$BASE_DIR/src/u-boot"
UBOOT_BIN="$ARTIFACTS_DIR/u-boot.bin"

OPENWRT_VER="19.07.8"
OPENWRT_DIR="$BASE_DIR/src/openwrt"
OPENWRT_KERNEL="$ARTIFACTS_DIR/openwrt-kernel.bin"
OPENWRT_ROOTFS="$ARTIFACTS_DIR/openwrt-rootfs.tar.gz"

SD_IMAGE_FILE="$OUT_DIR/BPI-R2_SD.img"
EMMC_BOOT0_FILE="$OUT_DIR/BPI-R2_EMMC_boot0.img"
EMMC_IMAGE_FILE="$OUT_DIR/BPI-R2_EMMC.img"'

# evaluate the above string (e.g. resolve paths)
while IFS='=' read -r key temp || [ -n "$key" ]; do
    # ignore "empty" lines
    case "$key" in
	'')
		continue
		;;
	esac

    value=$(eval echo "$temp")
    eval export "$key='$value'"
	echo "$key=$value" >> .env
done <<< "$build_environment"