zshのプロンプトにrvmのRubyを表示する

autoload -Uz vcs_info
zstyle ':vcs_info:*' formats '(%s)-[%b]'
zstyle ':vcs_info:*' actionformats '(%s)-[%b|%a]'
precmd () {
    psvar=()

    # for vcs_info
    LANG=en_US.UTF-8 vcs_info
    [[ -n "$vcs_info_msg_0_" ]] && psvar[1]="$vcs_info_msg_0_"

    # for rvm
    [[ -n "$rvm_ruby_string" ]] && psvar[2]="$rvm_ruby_string"

    # for gemset
    ind=$(expr index $GEM_HOME $rvm_gemset_separator)
    if [ $ind -ne 0 ]; then
        length="$(expr length $GEM_HOME)"
        sub_length=`expr $length - $ind + 1`
        gem_spec=`expr substr $GEM_HOME $ind $sub_length`
        [[ -n "$psvar[2]" ]] && psvar[2]="$psvar[2]$gem_spec"
    fi
}
VCS_PROMPT="%1(v|%F{green} %1v%f|)"
RUBY_PROMPT="%2(v| %U%B%F{magenta}(%2v)%f%b%u|)"
PROMPT=$'%{\e[32m%}$LOGNAME@${WINDOW:+"[$WINDOW]"}%B:%b%{\e[m%}[%~]$RUBY_PROMPT$VCS_PROMPT\n%% '