Adaptive Ruby version when opening a terminal - ruby-on-rails

Question

This question is the opposite of this one (also asked here, here and here)
I have two versions of ruby installed
ubuntu:~/environment $ rvm list
ruby-2.6.6 [ x86_64 ]
=* ruby-3.0.2 [ x86_64 ]
and every time I open a terminal window, ruby-3.0.2 (the default) is set. The problem is for a couple of my older projects I have to use ruby-2.6.6, so every time I have to switch with
rvm use 2.6.6
Is there a way to automatically select ruby 2.6.6 when I open the terminal window of the specific projects? I have tried to override the default rvm version with the .ruby-version file (as suggested here) but it does not do the trick.
EDIT File /home/ubuntu/.rvm/scripts/cd contains the following
#!/usr/bin/env bash
# Source a .rvmrc file in a directory after changing to it, if it exists. To
# disable this feature, set rvm_project_rvmrc=0 in /etc/rvmrc or $HOME/.rvmrc
case "${rvm_project_rvmrc:-1}" in
1|cd)
# cloned from git#github.com:mpapis/bash_zsh_support.git
source "$rvm_scripts_path/extras/bash_zsh_support/chpwd/function.sh"
# not using default loading to support older Zsh
[[ -n "${ZSH_VERSION:-}" ]] &&
__rvm_version_compare "$ZSH_VERSION" -gt 4.3.4 ||
{
function cd() { __zsh_like_cd cd "$#" ; }
function popd() { __zsh_like_cd popd "$#" ; }
function pushd() { __zsh_like_cd pushd "$#" ; }
}
__rvm_after_cd()
{
\typeset rvm_hook
rvm_hook="after_cd"
if [[ -n "${rvm_scripts_path:-}" || -n "${rvm_path:-}" ]]
then source "${rvm_scripts_path:-$rvm_path/scripts}/hook"
fi
}
__rvm_cd_functions_set()
{
__rvm_do_with_env_before
if [[ -n "${rvm_current_rvmrc:-""}" && "$OLDPWD" == "$PWD" ]]
then rvm_current_rvmrc=""
fi
__rvm_project_rvmrc >&2 || true
__rvm_after_cd || true
__rvm_do_with_env_after
return 0
}
[[ " ${chpwd_functions[*]} " == *" __rvm_cd_functions_set "* ]] ||
chpwd_functions=( "${chpwd_functions[#]}" __rvm_cd_functions_set )
# This functionality is opt-in by setting rvm_cd_complete_flag=1 in ~/.rvmrc
# Generic bash cd completion seems to work great for most, so this is only
# for those that have some issues with that.
if (( ${rvm_cd_complete_flag:-0} == 1 ))
then
# If $CDPATH is set, bash should tab-complete based on directories in those paths,
# but with the cd function above, the built-in tab-complete ignores $CDPATH. This
# function returns that functionality.
_rvm_cd_complete ()
{
\typeset directory current matches item index sep
sep="${IFS}"
export IFS
IFS=$'\n'
COMPREPLY=()
current="${COMP_WORDS[COMP_CWORD]}"
if [[ -n "$CDPATH" && ${current:0:1} != "/" ]] ; then
index=0
# The change to IFS above means that the \command \tr below should replace ':'
# with a newline rather than a space. A space would be ignored, breaking
# TAB completion based on CDPATH again
for directory in $(printf "%b" "$CDPATH" | \command \tr -s ':' '\n') ; do
for item in $( compgen -d "$directory/$current" ) ; do
COMPREPLY[index++]=${item#$directory/}
done
done
else
COMPREPLY=( $(compgen -d ${current}) )
fi
IFS="${sep}";
}
complete -o bashdefault -o default -o filenames -o dirnames -o nospace -F _rvm_cd_complete cd
fi
;;
2|prompt)
if
[[ -n "${ZSH_VERSION:-}" ]]
then
precmd_functions+=(__rvm_do_with_env_before __rvm_project_rvmrc __rvm_do_with_env_after)
else
PROMPT_COMMAND="${PROMPT_COMMAND%% }"
PROMPT_COMMAND="${PROMPT_COMMAND%%;}"
PROMPT_COMMAND="${PROMPT_COMMAND:-}${PROMPT_COMMAND:+; }__rvm_do_with_env_before; __rvm_project_rvmrc; __rvm_do_with_env_after"
fi
;;
esac

Answer 1

You are probably using RVM as a shell script, and not as a shell function.
You can check like this in a typical shell (bash, zsh, ...) : execute: type rvm
If it displays rvm is /home/ying/.rvm/bin/rvm : you are using as a script (found in $PATH)
If it displays rvm is a function : you are using as a function (much better).
Check out: https://rvm.io/rvm/basics#post-install-configuration
If you are using as a script, and want to use as a function: you need to "source" the rvm function, it is located in <rvm main folder>/scripts/rvm, for instance if installed in $HOME:
source $HOME/.rvm/scripts/rvm
source /usr/local/rvm/scripts/rvm
Typically, at RVM installation time, it add the following line in the equivalent of .profile (depending on shell and if its global or user):
[[ -s "$HOME/.rvm/scripts/rvm" ]] && source "$HOME/.rvm/scripts/rvm" # Load RVM into a shell session *as a function*
RVM changes automatically the version as described here:
https://rvm.io/workflow/projects
For detection of .ruby-version, the following is required:
RVM must be a recent version that supports the feature
RVM must be loaded in the shell (typically by .profile, or equivalent) so that is is executed as a function
the shell must be compatible with this callback feature (bash and zsh are)
Here is what happens:
When you load rvm as a function, it registers callback in the shell
when you cd into the project, RVM callbacks (in shell) detect the file .ruby-version (or others) and automatically do the equivalent of rvm use.
For instance, I use zsh (on osx) which has preexec and precmd callbacks
and it detect the ruby version file and applies when I cd into it or a sub folder.
It works with bash too.
If you are curious or want to see why it does not work for you look at the file <rvm main dir>/scripts/cd
typically the shell variable chpwd_functions is set to __rvm_cd_functions_set
which is the function called after a cd by rvm