bin/153012: iostat(8) requires an argument to -c option

[Bruce Evans]

On Fri, 10 Dec 2010, Warren Block wrote:

>> Description:
> iostat(8) says:
>
> -c    Repeat the display count times.  If no repeat count is specified,
>      the default is infinity.

This used to be correct.  It said "if no wait interval is specified, then
the default [for the wait interval] is 1 second".  This was a bit confusing
since it didn't say that the default is for the wait interval.  Now it is
just broken, since it is the -c option and not its repeat count that is
optional.

> But if you try to run it without a repeat count:
>
> % iostat -c
> iostat: option requires an argument -- c
> usage: iostat [-CdhIKoTxz?] [-c count] [-M core] [-n devs] [-N system]
> 	      [-t type,if,pass] [-w wait] [drives]

The synopsis and usage message correctly specify that -c must have an arg.

The -w option has the complement of this breakage.

Either -w wait or the the normal way using the undocumented alias for this
("iostat wait", where `wait is a number') must be used to specifiy the wait
time for -c.  Not documenting this may be intentional, but it became
especially broken when the `drives' option was added, since according to
the synopsis and usage message "iostat 1" says to give statistics for the
drive named "1", but it is actually an alias for "iostat -w 1".

Bruce