Makefile中docker.*伪目标含义及%通配符作用咨询

Let’s break down your question into clear, actionable parts to demystify what’s happening here.

1. What does the docker.% phony target mean? #

First, .PHONY is a Makefile directive that tells Make: "This target isn’t a real file on your system." Even if a file named docker.my-app exists in your directory, Make will still execute the rule for this target instead of checking if the file is "up-to-date."

The docker.% is a pattern phony target—it’s not a single fixed target, but a template that matches any target starting with docker. (like docker.api, docker.test-service, or docker.my-app). This lets you reuse the exact same rule logic for multiple Docker-related tasks without writing duplicate code for each one.

2. What is % and how does it work in this rule? #

The % is Make’s pattern-matching wildcard. Here’s how it operates in your rule:

• When you run a command like make docker.my-app, the % in docker.% captures the part after docker.—so in this case, my-app.
• Make stores this captured text in the automatic variable $*, which you can reference later in the rule’s commands.

Let’s walk through the full execution flow when you run make docker.my-app:

1. First, it runs go mod tidy to sync and clean up your Go module dependencies.
2. Next, docker build -t $* . expands to docker build -t my-app .—this builds a Docker image tagged my-app using the Dockerfile in your current directory.
3. Finally, the docker run command becomes:

   docker run -p 5751:5751 -v $(pwd)/:/work my-app /work/config.yaml
   

   The $$(pwd) is an escape for $ (since Make uses $ for variables), so the shell receives $(pwd)—this mounts your current working directory into the container’s /work folder. The container runs the my-app image, uses /work/config.yaml as its config file, and maps port 5751 between your host machine and the container.

Quick example #

If you run make docker.hello-world, the rule will:

• Run go mod tidy
• Build an image tagged hello-world
• Spin up a container from that image with the port mount and config file specified

This pattern is incredibly handy because it lets you define one rule that works for any number of Docker images—just append your desired image name to docker. when you run make.

内容的提问来源于stack exchange，提问作者Behrang Saeedzadeh