Get ruby version from a project regardless of version manager used

rbversion.sh

#!/bin/bash

echo 'Checking for ruby version in $RBENV_VERSION env var...'
if [ -n "$RBENV_VERSION" ]; then
  VERSION=$RBENV_VERSION
fi

if [ -z ${VERSION+x} ]; then
  echo 'Checking for ruby version in .ruby-version file...'
  if [ -f ./.ruby-version ]; then
    VERSION=`cat .ruby-version | tr -d '\n'`
  fi
fi

if [ -z ${VERSION+x} ]; then
  echo 'Checking for ruby version in .rvmrc file...'
  if [ -f ./.rvmrc ]; then
    [[ `cat .rvmrc | sed -e 's/\s*#[^!].*$//'` =~ environment_id\=[\'\"]([^\'\"]*)[\'\"] ]] && VERSION=${BASH_REMATCH[1]}
  fi
fi

if [ -z ${VERSION+x} ]; then
  echo 'Checking for ruby version in Gemfile...'
  if [ -f ./Gemfile ]; then
    [[ `cat Gemfile | sed -e 's/\s*#[^!].*$//'` =~ [^#][[:space:]]*ruby[[:space:]]*[\'\"]([^\'\"]*)[\'\"] ]] && VERSION=${BASH_REMATCH[1]}
  fi
fi

if [ -z ${VERSION+x} ]; then
  echo 'NO RUBY VERSION FOUND!'
  exit
fi

echo "$VERSION found!"

## Un-comment to use RVM
#
# rvm install $VERSION
# rvm use $VERSION

## Un-comment to use rbenv
#
# rbenv install $VERSION
# rbenv global $VERSION