Makefile: reading environment variables from `.env`-CodePudding

I want to check if the following is the correct/acceptable way of reading environment variables from .env in a Makefile.

Makefile:

export DB_HOST=$(shell grep DB_HOST .env | cut -d '=' -f2)
export DB_PORT=$(shell grep DB_PORT .env | cut -d '=' -f2)
export DB_NAME=$(shell grep DB_NAME .env | cut -d '=' -f2)
export DB_PASSWORD=$(shell grep DB_PASSWORD .env | cut -d '=' -f2)
export DB_CONTAINER_NAME=$(shell grep DB_CONTAINER_NAME .env | cut -d '=' -f2)

.PHONY: run-mysql-database
run-mysql-database:
    @docker run --name $(DB_CONTAINER_NAME) -p $(DB_PORT):3306 -e MYSQL_ROOT_PASSWORD=$(DB_PASSWORD) -e MYSQL_DATABASE=$(DB_NAME) -d mysql

Content of .env:

DB_HOST=localhost
DB_PORT=13306
DB_NAME="spring-boot-todo"
DB_PASSWORD="password"
DB_CONTAINER_NAME="spring-boot-todo-db"

I also tried to use another approach — introduce init target and call it before executing run-mysql-database. But this approach does not work:

init:
    source .env
    export DB_HOST
    export DB_PORT
    export DB_NAME
    export DB_PASSWORD
    export DB_CONTAINER_NAME

Error: make: source: No such file or directory

Another option is to use source .env before executing a command:

# run Spring Boot application
.PHONY: run
run: run-mysql-database
    # set environment variables from .env file and run Spring Boot application
    @echo "Running Spring Boot application..."
    @source .env && ./mvnw spring-boot:run

This works. But sometimes, I need to access a specific environment variable (e.g., for printing) and wonder if there is a better approach.

CodePudding user response：

As @Beta mentioned in his comment, you just need to write include .env at top of your Makefile and it should include the variables declared in .env file.

Showing a very simple and working example (Files and example taken from https://www.cs.colby.edu/maxwell/courses/tutorials/maketutor/):

Contents of your .env file:

Makefile-Test$ cat .env
DB_HOST=localhost
DB_PORT=13306
DB_NAME="spring-boot-todo"
DB_PASSWORD="password"
DB_CONTAINER_NAME="spring-boot-todo-db"

And Contents of Makefile:

include .env
hellomake: hellomake.c hellofunc.c
    @echo ${DB_HOST}
    gcc -o hellomake hellomake.c hellofunc.c -I.

clean:
    @echo ${DB_NAME}
    rm -f hellomake

all: clean hellomake

Running make all should first print the contents of variable DB_NAME and then DB_HOST.