curl
在命令列上顯示進度,如下所示:
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
8 1000M 8 85.2M 0 0 57k 0 1:06:13 0:05:38 1:00:35 47k
本例所示的速度為47k
。但是,這是什麼意思?這是:
- 47KiB,即47 * 1024字節
- 47kB,即47*1000字節
- 47kb,即47 * 1000位元(位元常用於衡量速度)
是嗎:
- 每秒
- 或每分鐘?
答案1
curl 使用什麼單位表示頻寬?
根據原始碼這是KiB per second
。
在這裡你可以看到定義使用1024
而不是1000
/* The point of this function would be to return a string of the input data,
but never longer than 5 columns (+ one zero byte).
Add suffix k, M, G when suitable... */
static char *max5data(curl_off_t bytes, char *max5)
{
#define ONE_KILOBYTE CURL_OFF_T_C(1024)
#define ONE_MEGABYTE (CURL_OFF_T_C(1024) * ONE_KILOBYTE)
#define ONE_GIGABYTE (CURL_OFF_T_C(1024) * ONE_MEGABYTE)
#define ONE_TERABYTE (CURL_OFF_T_C(1024) * ONE_GIGABYTE)
#define ONE_PETABYTE (CURL_OFF_T_C(1024) * ONE_TERABYTE)
...
}
在這裡您可以看到計算以毫秒為單位完成,然後除以1000
秒即可獲得。
/* Calculate the average speed the last 'span_ms' milliseconds */
{
curl_off_t amount = data->progress.speeder[nowindex]-
data->progress.speeder[checkindex];
if(amount > CURL_OFF_T_C(4294967) /* 0xffffffff/1000 */)
/* the 'amount' value is bigger than would fit in 32 bits if
multiplied with 1000, so we use the double math for this */
data->progress.current_speed = (curl_off_t)
((double)amount/((double)span_ms/1000.0));
else
/* the 'amount' value is small enough to fit within 32 bits even
when multiplied with 1000 */
data->progress.current_speed = amount*CURL_OFF_T_C(1000)/span_ms;
}