Bash function to go up 1 or more directories without manually cd-ing

up.sh

function up {
    if [ -z "$1" -o ! "$1" -gt 0 ]; then
        cd ..
    else
        CDSTR=""
        for i in $(seq 1 $1) ; do
            CDSTR="../$CDSTR"
        done
        cd $CDSTR
    fi
}