Use #!/usr/bin/env bash instead of #!/bin/bash

[jcoetzee]

macOS ships with an old version of bash that doesn't recognise declare -A. Using /usr/bin/env bash instead of referencing /bin/bash directly allows macOS users to use homebrew supplied bash instead of the built-in one.

[karianna]

What happens if that doesn't exist?

[jonpspri]

#!/usr/bin/env bash will run whichever bash is first in the path, which usually should not present a problem unless it's a really old bash. On the other hand, I wouldn't suggest putting bash 4-isms into the scripts unless we really need them. Most systems have at least bash 3.

[jcoetzee]

Agreed that using Bash 4 features excludes macOS users from being able to build the images without some extra work. But then again Bash 4 is almost 10 years old now (released 20 Feb 2009) and it is possible for macOS users to install an up-to-date version. If you're building Docker on macOS then you probably have homebrew (or similar) installed already. There should just be some documentation around the requirement.

[karianna]

Our policy for Adopt infra is to stick with Bash 3 because of the OS X reason. I think we'd at least want a documentation update if the docker images are going to support Bash 4

[jonpspri]

As a side note, I’m updating slim-java.sh to be compatible with bash or dash (thank heavens for ShellCheck), which should eliminate the need to apk-get bash in the Alpine images. The changes are done and tested. I just need to extricate them into a separate branch for a PR... likely within the next few hours.

[karianna]

@dinogun Not sure whether we should merge this or not - thoughts?

[grzesuav]

I would say it is more elegant way of running script - not to focus on specific binary.

From the other side - why not just require to install bash4 on mac ? It does not seems like big issue (https://itnext.io/upgrading-bash-on-macos-7138bd1066ba)

[karianna]

I would say it is more elegant way of running script - not to focus on specific binary.

From the other side - why not just require to install bash4 on mac ? It does not seems like big issue (https://itnext.io/upgrading-bash-on-macos-7138bd1066ba)

Mac OS X 10.10 doesn't support modern HomeBrew and I think it's difficult to therefore install bash4+

[jcoetzee]

From the homebrew docs

10.12 or higher is recommended. 10.9–10.11 are supported on a best-effort basis.

Also Docker for Mac requires 10.12 anyway.

[jcoetzee]

I would say it is more elegant way of running script - not to focus on specific binary.

From the other side - why not just require to install bash4 on mac ? It does not seems like big issue (https://itnext.io/upgrading-bash-on-macos-7138bd1066ba)

Maybe I'm misunderstanding you but that howto guide also installs bash4+ via homebrew which I what I did. Important to note that this won't replace the OS bundled one at /bin/bash but will install to /usr/local/bin/bash. This commit will need to be merged for homebrew installed bash to be referenced over OS bundled one.

[karianna]

From the homebrew docs

10.12 or higher is recommended. 10.9–10.11 are supported on a best-effort basis.

Also Docker for Mac requires 10.12 anyway.

In that case we're probably OK to do this.