linux - How to grep download speed from wget output?

Question

I need to download several files with wget and measure download speed.

e.g. I download with

wget -O /dev/null http://ftp.bit.nl/pub/OpenBSD/4.7/i386/floppy47.fs http://ftp.bit.nl/pub/OpenBSD/4.7/i386/floppyB47.fs

and the output is

--2010-10-11 18:56:00--  http://ftp.bit.nl/pub/OpenBSD/4.7/i386/floppy47.fs
Resolving ftp.bit.nl... 213.136.12.213, 2001:7b8:3:37:20e:cff:fe4d:69ac
Connecting to ftp.bit.nl|213.136.12.213|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 1474560 (1.4M) [text/plain]
Saving to: `/dev/null'

100%[==============================================================>] 1,474,560    481K/s   in 3.0s

2010-10-11 18:56:03 (481 KB/s) - `/dev/null' saved [1474560/1474560]

--2010-10-11 18:56:03--  http://ftp.bit.nl/pub/OpenBSD/4.7/i386/floppyB47.fs
Reusing existing connection to ftp.bit.nl:80.
HTTP request sent, awaiting response... 200 OK
Length: 1474560 (1.4M) [text/plain]
Saving to: `/dev/null'

100%[==============================================================>] 1,474,560    499K/s   in 2.9s

2010-10-11 18:56:06 (499 KB/s) - `/dev/null' saved [1474560/1474560]

FINISHED --2010-10-11 18:56:06--
Downloaded: 2 files, 2.8M in 5.9s (490 KB/s)

I need to grep the total download speed, that is, the string 490 KB/s. How do I do this?

P.S. May need to account for the case that we will actually download only one file, so there won't be final output starting with FINISHED

Answer 1

Update, a grep-style version using sed:

wget ... 2>&1 | sed -n '$,$s/.*((.*)).*/1/p'

Old version:

I thought, it's easier to divide the file size by the download time after the download. ;-)

(/usr/bin/time -p wget ... 2>&1 >/dev/null; ls -l newfile) | 
awk '
   NR==1 {t=$2};
   NR==4 {printf("rate=%f bytes/second
", $5/t)}
'

The first awk line stores the elapsed real time of "real xx.xx" in variabe t. The second awk line divides the file size (column 5 of ls -l) by the time and outputs this as the rate.