go up by number means that do cd.. by number

go-up

# up 4 -> go up 4 directories
up()
{
    dir=""
    if [[ $1 =~ ^[0-9]+$ ]]; then
        x=0
        while [ $x -lt ${1:-1} ]; do
            dir=${dir}../
            x=$(($x+1))
        done
    else
         dir=..
    fi
    cd "$dir";
}