Adaptive Ruby version when opening a terminal

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