利用台銀匯率頁面提供的下載文字檔，抓取外幣現金賣出匯率
sh get_exchange_rate.sh
{"USD":"31.66200","HKD":"4.10100","GBP":"40.06000","AUD":"24.17000","CAD":"24.10000","SGD":"23.16000","CHF":"32.41000","JPY":"0.30560","ZAR":"0.00000","SEK":"3.76000","NZD":"22.73000","THB":"0.94080","PHP":"0.73550","IDR":"0.00278","EUR":"35.42000","KRW":"0.03038","VND":"0.00154","MYR":"8.09900","CNY":"4.75400"}