# see if we already cached the grep alias in past day
_grep_alias_cache=("$ZSH_CACHE_DIR"/grep_alias.zsh(Nm-24))
if (( $#_grep_alias_cache )); then
    source "$ZSH_CACHE_DIR"/grep_alias.zsh
else
    # is x grep argument available?
    grep-flags-available() {
        echo | grep "$@" "" >/dev/null 2>&1
    }

    GREP_OPTIONS=""

    # ignore these folders (if the necessary grep flags are available)
    EXC_FOLDERS="{.bzr,CVS,.git,.hg,.svn,.idea,.tox}"

    if grep-flags-available --color=auto --exclude-dir=.cvs; then
        GREP_OPTIONS+="--color=auto --exclude-dir=$EXC_FOLDERS"
    elif grep-flags-available --color=auto --exclude=.cvs; then
        GREP_OPTIONS+="--color=auto --exclude=$EXC_FOLDERS"
    elif grep-flags-available --color=auto; then
        GREP_OPTIONS+="--color=auto"
    fi

    {
        if [[ -n "$GREP_OPTIONS" ]]; then
            # export grep, egrep and fgrep settings
            echo alias grep="'grep $GREP_OPTIONS'"
            echo alias egrep="'egrep $GREP_OPTIONS'"
            echo alias fgrep="'fgrep $GREP_OPTIONS'"
        fi
    } > "$ZSH_CACHE_DIR/grep_alias.zsh"

    source "$ZSH_CACHE_DIR/grep_alias.zsh"

    # clean up
    unset GREP_OPTIONS EXC_FOLDERS
    unfunction grep-flags-available
fi
unset _grep_alias_cache