#! /usr/bin/env considered harmful - General Shell Scripting
jkl
venam
This is highly informative.
Next week podcast is about "default programs", I've added the subtitle: "Welcome to hell, choose your default program!".

I've only scrapped the subject so far, just prior knowledge, but it's not looking good, it's a mess.
z3bra
That space between the bang and path is bothering me...
IMO, the only VALID bang you should rely on is #!/bin/sh. Every single bit of it is defined by POSIX, and is made for portability.
josuah

On android, #!/bin/sh does not even works, as there is no /bin at all.

Such a bad OS for command line, but the projects for pocketable devices running linux are so rare these days!

Alternative is to build its own with a raspberry.

Useful article, as I was not aware of these issues.
robotchaos
@josuah, what about tizen?

EDIT: taking this off topic...

I wish my corp firewall didn't block github. I'd really like to read this. Will read it soon though
jkl
(14-09-2016, 01:36 PM)z3bra Wrote: That space between the bang and path is bothering me...

It's debatable if it was actually added intentionally or if it just "slipped through" in the affected BSD versions.
pranomostro
> Not the right interpreter is found

Generally we then have to ask for the better alternatives. If we specify a path, we can never be sure it works (because none of this shit is standartized, except the location of /usr/bin/env).

> No dependencies or modules

I can't say anything about that since the most things I use scripting for is either rc or lua, where I don't happen to need modules or dynamically linking libraries. Someone smarter than me comment on this please.

> no flags

This is really stupid. This is one of the stupid unix limitatians I talked about, things that don't make any sense today but are still included.
But it applies to other shebangs as well, so I would say fuck that.

> wrong configuration of $PATH

Then your user is a moron and it is his own fault. $PATH should never be changed, only appended to.

The solutions given are both bloated and unportable. env seems like the cleaner solution to me. I don't like using tho whole path since people thought it would be a good idea to put binaries into different directories. Ugh.
robotchaos
i) correct interpreter indeed. If you are on a shared server and are setting up a cron job that uses the absolute path to the python binary /usr/bin/python2.7, can you even still be sure that the executable is the one intended to complete the job? Or does shebanging absolutely give you checksumming powers?

ii) https://www.python.org/dev/peps/pep-0370/

iii) byoi(nterpreter)

iv) no flags? fine, don't use shebang on interpreted scripts. $ /usr/bin/python2.7 -RE ~/myscript

v) manage $PATH -- I fail to see the problem

vi) I feel like #!/usr/bin/env is suitable in the most properly configured environments; and in that case, more suited

Good read though :)
z3bra
(14-09-2016, 05:34 PM)josuah Wrote: On android, #!/bin/sh does not even works, as there is no /bin at all.

Android is not a POSIX Operating System, that's why :)
TheAnachron
I actually agree with pranomostro. That article also seems to be mosty linked to Python.
I use #!/usr/bin/env very often. It makes the user flexible to do as he wish.
If he messes this one up, it's not up to the programmer.




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