It’s a Docker shebang. Normally shebangs are used to define what shell to use when running a script, or in the case of a python script, to run it with “./myscript” instead of “python myscript.py”.

Here OP created a little hack for building and running a docker container by adding a shebang to a Dockerfile.

Usually it’s a two step process. You first use “docker build” to build the image and then “docker run” to create a container from it. With this little hack you just run “./Dockerfile” and it does both.

It’s cool, but not really useful for most people.

It turns a Dockerfile into an executable script, so that by executing the Dockerfile, the shebang invokes docker to build and run the file.

Pretty neat if you're using Dockerfiles, but also highly non-standard so you wouldn't use it in your company repo (unless you want to increase the "what-the-fuck" level of your repo).

It's more of a "look, this is cool" kind of a thing if you're a Linux and container user.