function cd_history () {
    if [ -z "$1" ]
    then \cd "$HOME"
         return
    fi
    old=$( tail -n 149 "$HOME/.bash_cdhistory" )
    echo "$old" > "$HOME/.bash_cdhistory"
    \cd "$1"
    p=$( pwd )
    b=$( basename "$p" )
    echo $b":"$p >> "$HOME/.bash_cdhistory"
}
alias cd=cd_history

function qcd() {
    while getopts alhm opt
    do  case "$opt" in
        a)
            # Adding
            name=${!OPTIND}
            if [ -z "$name" ]
            then name=$( basename $( pwd ))
            fi

            echo "$name":$( pwd )
            echo "$name":$( pwd ) >> ~/.qcd
        ;;
        l)
             echo ==History ~/.bash_cdhistory:
             cat ~/.bash_cdhistory
             echo 
             echo ==Saved ~/.qcd:
             cat ~/.qcd
        ;;
        m)
            IFS=$'\n'
            for line in $( cat ~/.bash_cdhistory );
            do if [ -d "${line/*:/}" ];
               then echo "$line" >> ~/.bash_cdhistory.tmp
               fi
            done
            mv ~/.bash_cdhistory.tmp ~/.bash_cdhistory
            for line in $( cat ~/.qcd );
            do if [ -d "${line/*:/}" ];
               then echo "$line" >> ~/.qcd.tmp
               fi
            done
            mv ~/.qcd.tmp ~/.qcd
        ;;
        h)
            echo "qcd [-al] [name]"
            echo "Change current working path based on the list ~/.qcd"
            echo "Keeps a history of folders visited in ~/.bash_cdhistory"
            echo " "
            echo "qcd -a [name]"
            echo "  Adds the path to the list"
            echo "  You may add the name of the path, but when omitted"
            echo "  the basename will be used"
            echo " "
            echo "qcd -l "
            echo "  Lists the paths"
            echo " "
            echo "qcd -m "
            echo "  Maintain the list files, deleting non-existing entries"
        ;;
        esac
    done
    unset OPTSTRING
    unset OPTIND
    if [ -z "$1" ]
    then \cd
    else
     d=$( grep -h ^"$1" ~/.qcd <( tac ~/.bash_cdhistory ) | head -n 1 )
     d=${d/*:/}
     if [ ! -z "$d" ]
     then \cd "$d" 
     fi
    fi
}


function whenfilechanges() {
    [ -z "$1" ] && { echo 'Usage: whenfilechanges "file" "some" "command" 
      Follows the modification time of the "file" and runs the command 
      at every change.  '
        return
    }
    [ -e "$1" ] || { echo $1 not found
        return
    }
    
    fname=$1
    shift 1
    otime=$( stat -c %Z "$fname" )
    while : 
    do ntime=$( stat -c %Z "$fname" )
        [ "$ntime" -ne "$otime" ] && {
            eval "$@"
            otime=$( stat -c %Z "$fname" )
        }
        
       sleep 2
    done

}