[SOLVED] Install Latest Stable Version of Ruby Using rbenv

Issue

I want to install the latest stable version of Ruby available with rbenv. This feature href="https://github.com/sstephenson/ruby-build/issues/276">won't be happening in rbenv itself.

When I run the command rbenv install -l in my shell, I get a long list of available versions. The list has all types of entries. The following is a partial list to demonstrate the format and diversity:

$ rbenv install -l
Available versions:
  2.0.0-p643
  2.0.0-p645
  2.1.0-dev
  2.1.0-preview1
  2.1.0-preview2
  2.1.0-rc1
  2.1.4
  2.1.5
  2.1.6
  2.2.0-dev
  2.2.0-preview1
  2.2.0-preview2
  2.2.0-rc1
  2.2.0
  2.2.1
  2.2.2
  2.3.0-dev
  jruby-1.7.19
  jruby-1.7.20
  jruby-9.0.0.0-dev
  jruby-9.0.0.0+graal-dev
  jruby-9.0.0.0.pre1
  jruby-9.0.0.0.pre2
  maglev-1.0.0
  maglev-1.1.0-dev
  maglev-2.0.0-dev
  mruby-dev
  mruby-1.0.0
  mruby-1.1.0
  rbx-2.5.2
  rbx-2.5.3
  ree-1.8.7-2011.12
  ree-1.8.7-2012.01
  ree-1.8.7-2012.02
  topaz-dev

My goal is to automate the command rbenv install VERSION in a shell script where VERSION is the highest x.x.x release. In other words, I need to automatically substitute the highest entry on the list that starts with a number and does not end with -something into VERSION. From this list, I need 2.2.2.

What can I put in my shell script to automatically pick the highest x.x.x version in the command rbenv install x.x.x?

Edit: Since Ruby is not yet installed, the solution has to be in Bash and not Ruby.

Edit 2: I want the MRI (mainstream) version of Ruby.

Solution

rbenv install -l | awk -F '.' '
   /^[[:space:]]*[0-9]+\.[0-9]+\.[0-9]+[[:space:]]*$/ {
      if ( ($1 * 100 + $2) * 100 + $3 > Max ) { 
         Max = ($1 * 100 + $2) * 100 + $3
         Version=$0
         }
      }
   END { print Version }'

• Take the biggest version (sorted order or not)

If list is sorted a simpler sed (posix version) is enough

rbenv install -l | sed -n '/^[[:space:]]*[0-9]\{1,\}\.[0-9]\{1,\}\.[0-9]\{1,\}[[:space:]]*$/ h;${g;p;}'

Answered By - NeronLeVelu

Answer Checked By - Katrina (WPSolving Volunteer)