A bash script that can source its required environment variables from an env file and re-execute itself

.env

export TEST_VAL_A=1
export TEST_VAL_B=2

check_env.sh

#!/bin/bash

# --------------
# Pre-run environment variable checks

if [[ -z $REQUIRED_ENVS ]]; then
	echo "'REQUIRED_ENVS' array is required to run pre-checks, exiting..."
	exit 1
fi

SCRIPT_NAME="$0"
ENV_FILENAME=".env"

PARENT_DIR=$(dirname $SCRIPT_NAME)
ENV_FILE="$PARENT_DIR/$ENV_FILENAME"


check_envs () {
	echo "Running env variables check..."
	for env_var in "$@" ; do
		if [[ -z "${!env_var}" ]]; then
			echo "Error: '$env_var' required env variable not set or has empty value"
			echo
			return 1
		fi
	done
	echo "All required envs set"
	echo
}

check_env_file () {
	if [[ ! -e $ENV_FILE ]]; then
		echo "Env file '$ENV_FILE' does not exist, exiting..."
		exit 1
	fi

	echo "Checking '$ENV_FILE' for required envs..."
	for env_var in "$@" ; do
		if ! cat $ENV_FILE | grep -q "\b$env_var\b"; then
			echo "Error: '$env_var' required env variable not found in '$ENV_FILE'"
			echo
			return 1
		fi
	done
	echo "All required envs found in '$ENV_FILE'"
}

source_env_and_rerun () {
	if [[ -e $ENV_FILE ]]; then
		source $ENV_FILE
		$SCRIPT_NAME
		exit
	else
		echo "Env file '$ENV_FILE' does not exist, exiting..."
		exit 1
	fi
}


check_env_before_run () {
	if ! check_envs ${REQUIRED_ENVS[@]}; then
		if check_env_file ${REQUIRED_ENVS[@]}; then
			echo "Attempting source from $ENV_FILE"
			echo
			source_env_and_rerun
		else
			echo "Missing envs not found in '$ENV_FILE', exiting..."
			exit 1
		fi
	fi
}

check_env_before_run && \
	echo "----------" && \
	echo

run.sh

#!/bin/bash

# Do env variables check 1st
REQUIRED_ENVS=(\
	"TEST_VAL_A" \
	"TEST_VAL_B" \
	# "TEST_VAL_C" \
)

source check_env.sh

# --------------
# Actual script starts here

echo "Hello World:"

for env_var in ${REQUIRED_ENVS[@]}; do
	echo "  $env_var=${!env_var}"
done