Change PATH based on Gemfile

.bashrc

source "/home/judson/bin/bundler_ps1.sh"

if [[ ! $PROMPT_COMMAND =~ __bundler_prompt_command ]]; then
  export PROMPT_COMMAND="${PROMPT_COMMAND:-:} ; __bundler_prompt_command"
fi

PS1="\[\033[01;31m\]\$(__bundler_ps1)\[\033[01;34m\] $PS1"

bundle_setup.sh

#!/bin/sh

BUNDLE_BASE=~/ruby/bundle-paths/

if [ -f .bundle/config ]; then
  echo "Bundle config file already exists"
  bundle install
else
  projname=$(basename $(pwd))
  BUNDLE_PATH="$BUNDLE_BASE/lib"
  BINSTUBS=".bundle/bin"

  echo "Setting up bundle for $projname"
  bundle install --path=$BUNDLE_PATH --binstubs=$BINSTUBS
fi

bundler_ps1.sh

export bundle_dir=""
export bundle_bin=""
export orig_path=$PATH

function find_bundle_dir() {
  bundle_dir=$(pwd)
  while [ $bundle_dir != "/" ]; do
    if [ -e $bundle_dir/.bundle/config ]; then
      return 0
    fi
    bundle_dir=$(dirname $bundle_dir)
  done
  bundle_dir=""
  export bundle_dir
  echo $bundle_dir

  return 1
}

function bundle_config_changed() {
  local old_dir=$bundle_dir

  find_bundle_dir

  if [ "$bundle_dir" != "$old_dir" ]; then
    return 0
  else
    return 1
  fi
}


function __bundler_prompt_command(){
  if bundle_config_changed; then
    if [ ! -z "$bundle_bin" ]; then
      export PATH=$(echo $PATH | sed "s!${bundle_bin}\:!!")
    fi
    if [ -e $bundle_dir/.bundle/config ]; then
      export bundle_bin=$(cat $bundle_dir/.bundle/config | grep BUNDLE_BIN | awk '{ print $2 }')
    else
      export bundle_bin=""
    fi
  fi

  if echo $PATH | grep -q -v "$bundle_bin";  then
    export PATH=$bundle_bin:$PATH
  fi
}

function __bundler_ps1(){
  if [ ! -z "$bundle_bin" ]; then
    if echo $PATH | grep -q "$bundle_bin"; then
      echo -n 'B '
    fi
  fi
}

Which means...

judson@dijkstra /home/judson $ echo $PATH
~/bin:/usr/local/bin:/usr/bin:/bin:/opt/bin:/usr/i686-pc-linux-gnu/gcc-bin/4.5.3:/usr/games/bin

judson@dijkstra /home/judson $ cd ruby/gems/vizier/
B judson@dijkstra .../gems/vizier $ echo $PATH
/home/judson/ruby/bundle-paths/vizier/bin:~/bin:/usr/local/bin:/usr/bin:/bin:/opt/bin:/usr/i686-pc-linux-gnu/gcc-bin/4.5.3:/usr/games/bin
                                    
B judson@dijkstra .../gems/vizier $ cd ../../LRD/ecliptic/
B judson@dijkstra .../LRD/ecliptic (master) $ echo $PATH
/home/judson/ruby/bundle-paths/ecliptic/bin:~/bin:/usr/local/bin:/usr/bin:/bin:/opt/bin:/usr/i686-pc-linux-gnu/gcc-bin/4.5.3:/usr/games/bin

Thanks! I've been really pleased with it, and still use it today. Obviously, most of the credit goes to @wycats and the rest of the Bundler and Rubygems teams.

Since posting this gist, I made a little tweak to my .bashrc - I just updated the gist to reflect that change. The upshot is that now it'll work with other tools that modify PROMPT_COMMAND. Specifically, I use the very excellent autojump, which uses PROMPT_COMMAND to record pwd over time.

As to using multiple Rubys, there are a few answers - I think rbenv is a possiblity. My OS provides a utility to switch out components that mostly works (I'm less than thrilled with how it handles Passenger...) Full VMs will certainly swat that fly, though.

Yes: in a project, rake will run using the project's rake, etc. Likewise rails will run with the local Gemfile.

rake, rails and bundler are probably sufficient (rubygems is itself not precisely a gem) I sometimes install other gems just to get their rdoc installed, though.

The update looks great. I had not thought about other command_prompt tools. Though, I have an idea for one myself ;-)

I am so busy that I will not have time to try this out until the weekend. But I am definitely going to give a shot.

Again on the off topic system versus bundler gems. I suppose sometimes the designers are too close to their projects to explain the BIG picture to neophytes like myself, but I could not really get the idea that I had to use rails to make a rails project. Meaning that there are two levels of usage - it is a tool and "library". This became very confusing for me once I had more that one version of rails on my system. And I could not really find a doc or tutorial that clearly explained this -- and I have read a lot of them

I only just found out how to select which version of a system gem to run from the command line by passing its version number quoted by underscores. IOW, if I have rails 3.2.2, 3.1.11 and 2.3.5 installed as system gems I can build a new rails 2.3.5 project using:

rails _2.3.5_ my_app

OR a rails 3.1.11project using:

rails _3.1.11_ new myapp 

and plain:

rails new myapp

gets me a 3.2.2 project.

The irony is that I cannot find blurb where I read this again! I really do not want to test it until I can find some real documentation on it -- oh well, sorry for the side track...

Anyway I will let you know how it goes with your code next week. Thanks for implementing a great idea!