amd64/117664: iostat can't display IO current vlaue in first line

[chifeng]

>Number:         117664
>Category:       amd64
>Synopsis:       iostat can't display IO current vlaue in first line
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    freebsd-amd64
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          change-request
>Submitter-Id:   current-users
>Arrival-Date:   Tue Oct 30 07:30:02 UTC 2007
>Closed-Date:
>Last-Modified:
>Originator:     chifeng
>Release:        FreeBSD6.2-Release-p8
>Organization:
Platform Computing
>Environment:
FreeBSD cnxabuild.asia.corp.platform.com 6.2-RELEASE-p8 FreeBSD 6.2-RELEASE-p8 #0: Tue Oct 16 12:32:14 CST 2007     root at xabuild.asia.corp.platform.com:/usr/obj/usr/src/sys/PLATFORM  amd64
>Description:
When I write a shell script plugin for munin, I hope get a current value of IO statistics. But iostat can't do it, it first statistics that are printed are avaraged over the system uptime. If I use "iostat -c 2 | tail -1 " command, this will wait 2s at least. 
so I think for iostat first line, 1) iostat should be display current value, 2) have a parameter to display current value at least. 

# iostat -c 5
      tty             ad2             cpu
 tin tout  KB/t tps  MB/s  us ni sy in id
   0    2 16.48   1  0.01   0  0  0  0 100
   0  130 63.63 782 48.60   0  0 14  1 85
   0  104 62.68 594 36.38   2  0 24  0 73
   0   77 62.75 663 40.63   0  0 16  0 83
   0   67 24.65 1568 37.76   0  0 18  1 80
# iostat
      tty             ad2             cpu
 tin tout  KB/t tps  MB/s  us ni sy in id
   0    2 17.52   1  0.01   0  0  0  0 100
>How-To-Repeat:
iostat command.
>Fix:
:-( I don't know how to fix it.

>Release-Note:
>Audit-Trail:
>Unformatted: