bin/91034: minor fix to iostat so that columns line up with 128KB xfers

[Bruce Evans]

The following reply was made to PR bin/91034; it has been noted by GNATS.

From: Bruce Evans <bde at zeta.org.au>
To: Giorgos Keramidas <keramida at ceid.upatras.gr>
Cc: freebsd-gnats-submit at FreeBSD.org
Subject: Re: bin/91034: minor fix to iostat so that columns line up with
 128KB xfers
Date: Wed, 4 Jan 2006 13:09:02 +1100 (EST)

 On Tue, 3 Jan 2006, Giorgos Keramidas wrote:
 
 > On 2006-01-03 22:40, Bruce Evans <bde at zeta.org.au> wrote:
 >> On Tue, 3 Jan 2006, Giorgos Keramidas wrote:
 >>> On 2005-12-28 21:16, Robert Cousins <rec at RCousins.com> wrote:
 >>>> Iostat's output can be kind of ugly under USF2 with 128KB
 >>>> transfers. Here is an example:
 >>>> ...
 >>>> The patch I'm submitting notices when this value is >= 100 and
 >>>> drops from 2 decimals to 1 in this case. The result is an output
 >>>> like this:
 >>> ...
 >>> The misaligned dots seem a bit ugly.
 >> ...
 >>> Is it ok to use %6.2Lf as
 >>> the format specifier, widening the KB columns a bit to fit the
 >>> new length of the text?
 >>
 >> No.  There is space in the above, but most systems have more than 2 drives
 >> ...
 >
 > So, there's no way to keep the pretty format of current iostat output
 > *and* account for larger transfer speeds? :-(
 
 Maybe always drop %5.1Lf format for disk MB/s.  If the value is < 0.10
 MB/s then it is so low that you don't really care if it is 0.01 or 0.09.
 However, floppies have a top speed of about 0.04, and speeds below
 0.10 are all too common for faster disks doing too many seeks.
 
 > Looking at an awk-formatted version of the iostat output it seems that
 > even with 3 disks we *do* hae 3 columns to spare until 79 columns are
 > reached:
 >
 > $ iostat ad0 da0 pass0 | awk '{printf "%-78s|\n",$0}'
 >      tty             ad0              da0            pass0             cpu   |
 > tin tout  KB/t tps  MB/s   KB/t tps  MB/s   KB/t tps  MB/s  us ni sy in id   |
 >  63  514  7.10  13  0.09   0.01   0  0.00   0.00   0  0.00   1  0  2  0 96   |
 > $
 
 >
 > Is this enough for adding an extra column to every KB/t column and
 > still keeping everything under 80 columns?
 
 No, since there are actually only 2 columns to spare.  "id" sometimes
 takes an extra column since it is sometimes 100.  I hacked its format
 in rev.1.25 of iostat.c from %3.0f to " %2.0f".  The space keeps it
 from running into "in", and reducing the field width keeps the line
 length the same except when cpu is 100 when it doesn't fit in %2.0f.
 As mentioned in the log message for this, larger fixes are needed.
 I think they should be something like
 "iostat -w N | awk '{printf "%*.*s %*.*s ...\n", $1, $2, ...}'" where the
 awk script calculates the column widths dynamically and is actually
 a library function.  This should also work for ps and df.  It's easier
 for them since all the input can be read before doing any output.
 Except I'd like ps to have a "repeat" arg like iostat, for watching
 a few selected processes better than top(1) or repeatedly rerunning
 ps(1) can do.
 
 Bruce