chruby and ohmygems together at last

.profile

# my preferred prompt - ☣ [pairwithme:rails4] $
PS1='\[\e[1;31m\]☣ [\W$(if [ -n "$OMG_NAME" ]; then eval "echo :$OMG_NAME"; fi)] $\[\e[0m\] '

# chruby configuration
source /usr/local/share/chruby/chruby.sh
source /usr/local/share/chruby/auto.sh

# set default ruby
chruby 2.1

# ohmygems configuration
source ~/ohmygems.sh
source ~/ohmygems_chruby.sh

ohmygems.sh

# -*- sh -*-

ohmygems() {
    name=${1:-}

    if [ -z "${ORIG_GEM_PATH:-}" ]; then
        export ORIG_GEM_PATH=${GEM_PATH:-}
        export ORIG_GEM_HOME=${GEM_HOME:-}
        export ORIG_PATH=${PATH}
    fi

    if [ -z "$name" ]; then
        echo "usage: ohmygems <name or reset or env>"
        echo
        echo "  Switches gem home to a (potentially new) named repo."
        echo "  Your previous gems are still visible,"
        echo "  but new gem installs will install into ~/.gem/repos/<name>."
        echo "  Use 'reset' to go back to normal."
        echo "  Use 'env' to view environment information."
        echo
        echo "Available repos in ~/.gem/repos:"
        echo
        ls ~/.gem/repos | pr -o2 -l1
        echo
        return
    elif [ $name = "reset" ]; then
        echo Resetting repo

        if [ -z "$ORIG_GEM_HOME" ]; then
            unset GEM_HOME
        else
            GEM_HOME=${ORIG_GEM_HOME}
        fi

        GEM_PATH=${ORIG_GEM_PATH}
        PATH=$ORIG_PATH
        unset OMG_NAME
    elif [ $name = "env" ]; then
        echo Oh My Gems Environment

        echo GEM_PATH=${GEM_PATH:-not set}
        echo GEM_HOME=${GEM_HOME:-not set}
        echo PATH=$PATH
    else
        echo Switching to $name

        export GEM_HOME=~/.gem/repos/${name}
        export GEM_PATH=${ORIG_GEM_HOME}:${ORIG_GEM_PATH}
        export PATH=${ORIG_PATH}:${GEM_HOME}/bin

        [ -d $GEM_HOME ] || mkdir -p $GEM_HOME
        OMG_NAME=${name}
    fi
}

alias omg=ohmygems

ohmygems_chruby.sh

# Reload ohmygems when chruby is called.
# Inspired by chruby's after hook wiki:
# https://github.com/postmodern/chruby/wiki/Implementing-an-'after-use'-hook

save_function() {
    local ORIG_FUNC=$(declare -f $1)
    local NEWNAME_FUNC="$2${ORIG_FUNC#$1}"
    eval "$NEWNAME_FUNC"
}

save_function chruby ohmygems_chruby

function chruby () {
    # Are we in a gemset?
    omg_name=${OMG_NAME}

    # Reset ohmygems
    ohmygems reset
    # Including removing the ENV variables
    unset ORIG_GEM_PATH
    unset ORIG_GEM_HOME
    unset ORIG_PATH

    # Switch ruby
    ohmygems_chruby $*

    # Reload gem repo after switching rubies
    if [ -n "$omg_name" ]; then
        ohmygems ${omg_name}
    fi
}

shell

☣ [~] $ time ruby -v
ruby 2.0.0p247 (2013-06-27 revision 41674) [universal.x86_64-darwin13]

real	0m0.006s
user	0m0.004s
sys	0m0.002s
☣ [~] $ time rails -v
Rails is not currently installed on this system. To get the latest version, simply type:

    $ sudo gem install rails

You can then rerun your "rails" command.

real	0m0.042s
user	0m0.029s
sys	0m0.011s
☣ [~] $ chruby 1.9
☣ [~] $ time ruby -v
ruby 1.9.3p484 (2013-11-22 revision 43786) [x86_64-darwin13.0.0]

real	0m0.006s
user	0m0.003s
sys	0m0.002s
☣ [~] $ time rails -v
Rails is not currently installed on this system. To get the latest version, simply type:

    $ sudo gem install rails

You can then rerun your "rails" command.

real	0m0.039s
user	0m0.027s
sys	0m0.010s
☣ [~] $ omg rails4
Switching to rails4
☣ [~:rails4] $ time ruby -v
ruby 1.9.3p484 (2013-11-22 revision 43786) [x86_64-darwin13.0.0]

real	0m0.007s
user	0m0.003s
sys	0m0.002s
☣ [~:rails4] $ time rails -v
Rails 4.0.2

real	0m0.086s
user	0m0.054s
sys	0m0.028s
☣ [~:rails4] $ chruby 2.1
Switching to rails4
☣ [~:rails4] $ time ruby -v
ruby 2.1.0p0 (2013-12-25 revision 44422) [x86_64-darwin13.0]

real	0m0.008s
user	0m0.005s
sys	0m0.003s
☣ [~:rails4] $ time rails -v
Rails 4.0.2

real	0m0.084s
user	0m0.051s
sys	0m0.027s

My ohmygems changes:

• Fixed typo in usage
• Will now create the gem directory if needed
• Split env info out to omg env
• Store gem name in OMG_NAME, so I can display it in my prompt
• Prepended GEM_HOME to PATH instead of appending it

See @zenspider's original post for more information.