Set SHELL environment variable

[poetaman]

Environment variable SHELL is empty...

$ docker run --rm -it bitnami/minideb:bullseye bash -c 'echo $SHELL'
/bin/bash

$ docker run -it zshusers/zsh:5.8 zsh -c 'echo $SHELL'

EDIT: bitnami/minideb:bullseye's SHELL is a shell variable and not an environment variable. Not sure if it's a good idea to set environment variable SHELL. Neither is set by this image.