Poor man's ruby version manager

gistfile1.sh

# poor man's ruby version manager
# assume you have ZenTest installed
# usage:
#  rvm help
#  rvm list
#  rvm reset
#  rvm switch VERSION
#  rvm show

PRE_RVM_PATH=$PATH
MULTIRUBY_INSTALL_DIR=$HOME/.multiruby/install
RVM_COMMANDS="help list reset show switch"
function rvm {
    # set -x
    if [ ! -d $MULTIRUBY_INSTALL_DIR ]; then
        echo "rvm: $MULTIRUBY_INSTALL_DIR does not exist"
        echo "     consider installing ZenTest with 'gem install ZenTest'"
        return 1
    fi
    what=$1
    to=$2
    case $what in
        list)
        echo "installed:"
        for i in $(ls -d $MULTIRUBY_INSTALL_DIR/*); do
            echo "  ${i##*/}"
        done
        ;;
        reset)
        rvm switch default
        ;;
        switch)
        if [ -z $to ]; then
            echo "sepecify which ruby to switch to"
            rvm list
            return 1
        fi
        if [ $to = 'default' ]; then
            unalias ruby > /dev/null 2>&1 # don't care if 'ruby' alias exists or not
            export PATH=$PRE_RVM_PATH
            return 0
        fi
        if [ $(ls -1d $MULTIRUBY_INSTALL_DIR/${to}* 2>/dev/null | wc -l) = 1 ]; then
            BINDIR=$(ls -1d $MULTIRUBY_INSTALL_DIR/${to}* 2>/dev/null)/bin
        else
            BINDIR=$MULTIRUBY_INSTALL_DIR/$to/bin
        fi
        EXECUTABLE=''
        if [ -d $BINDIR ]; then
            if [ -x $BINDIR/ruby ]; then
                EXECUTABLE=$BINDIR/ruby
            else
                if [ -x $BINDIR/jruby ]; then
                    EXECUTABLE=$BINDIR/jruby
                else
                    if [ -x $BINDIR/rbx ]; then
                        EXECUTABLE=$BINDIR/rbx
                    fi
                fi
            fi
        else
            echo "rvm: cannot switch to $to"
            rvm list
            return 1
        fi
        if [ -z $EXECUTABLE ]; then
            echo "rvm: cannot switch to $to"
            rvm list
            return 1
        fi
        export PATH=$BINDIR:$PRE_RVM_PATH
        alias ruby=$EXECUTABLE
        ;;
        show)
        echo $(ruby -v)
        ;;
        *)
        retval=0
        if [ $what != "help" ]; then
            echo "rvm: do not know how to do $what"
            retval=1
        fi
        echo "  rvm list           - list installed versions"
        echo "  rvm reset          - undo rvm settings"
        echo "  rvm show           - show current ruby executable"
        echo "  rvm switch VERSION - change default ruby executable"
        return $retval
        ;;
    esac
}

function _rvm {
    local i c=1 command ver
    while [ $c -lt $COMP_CWORD ]; do
        i="${COMP_WORDS[c]}"
        command="$i"
        c=$((++c))
    done
    cur="${COMP_WORDS[COMP_CWORD]}"
    
    if [ -z "$command" ]; then
        COMPREPLY=($(compgen -W "$RVM_COMMANDS" -- "$cur")) && return
    fi
    
    case "$command" in
        switch)
        COMPREPLY=($(cd ${MULTIRUBY_INSTALL_DIR} >/dev/null; compgen -W "$(ls -d *)" -- "${COMP_WORDS[COMP_CWORD]}"))
        ;;
        *) COMPREPLY=()
        ;;
    esac
}

complete -o nospace -F _rvm rvm