Proper shebang for python3

[Chris Angelico]

On Mon, Jul 22, 2019 at 1:36 AM Tim Daneliuk <info at tundraware.com> wrote:
>
> On 7/21/19 8:47 AM, Peter J. Holzer wrote:
> > That's fine. Unlike Tim I don't claim that anybody who disagrees with me
> > must be a newbie.
>
> Peter, that's ad hominem and unfair.  I never said anything close to that.
> What I said is that if someone were to spend an extended period of time
> in devops and systems engineering at large scale, they'd quickly come to
> hate hardwired paths.
>
> The truth is that there is no single answer to this problem until you
> hermetically seal an environment.  Docker comes close, a freestanding
> VM does this most completely.   But short of that, the ability to decide
> to use something other than system-provided tools absolutely IS a requirement
> in systems of any scale.

Your final paragraph does not justify your preceding. Yes, you need
the ability to decide to use something other than the system-provided
tool; that's why "/usr/bin/env python3" is a valid shebang. No, that
does NOT mean that people with any decent experience will "hate
hardwired paths". The hardwired path ("#!/usr/bin/python3") has its
own value. Thanks to an absolute path in its shebang, I can run "sudo
iotop" regardless of whether I have a venv active. I cannot run "sudo
python3 `which iotop`" reliably, because that command uses the
environment to look things up.

You're absolutely right that there's no single answer to the problem.
That's why script authors have the option to use any path they like,
including /usr/bin/env.

ChrisA