What is the source of a "with-contenv" shebang?

Question

Could someone give me a brief explanation or links to an explanation of this topic? Info on the origination would be dandy. The only information that I could find is related to s6-overlay, which I have not yet used. Is this the origination of this?

of the use of this Shebang:

#!/usr/bin/with-contenv bash

vs. this Shebang:

#!/usr/bin/env bash

The second is what I use most of the time with bash.

The is a bash she-bang (shebang) question about a type of shebang.

#!/usr/bin/with-contenv bash
# your shellscript follows

#!/usr/bin/env bash
# this is my normal way of encoding the she-bang.

# Where to appropriately use?

I should note, that I did read "... just make use of with-contenv helper" and I was wondering if that is the first usage, or if it comes from another source like docker, w3c, or somewhere else.

Answer 1

Indeed, this is related, and very specific, to the s6-overlay architecture. This is a tool for using the s6 process supervisor inside of Docker containers.

In some more detail, Docker is otherwise not well-suited to running multiple services and daemons in the same container, and the general architecture of a supervisor is at odds with how Docker wants things. s6-overlay attempts to fix this, so that you can run services inside of a single Docker container.

As explained in the documentation, with-contenv is a wrapper which makes sure the argument is run with the environment variables specific to s6-overlay.

Concretely, it uses s6-envdir to load the environment from /var/run/s6/container_environment before executing its argument (in this case, bash).