svn commit: r184645 - head/usr.bin/vmstat

[Diomidis Spinellis]

Giorgos Keramidas wrote:
> On Tue, 4 Nov 2008 22:30:07 +0200, Diomidis Spinellis <dds at aueb.gr> wrote:
>> On Nov 4, 2008, at 8:02 PM, Giorgos Keramidas wrote:
>>> Author: keramida (doc committer)
>>> Date: Tue Nov  4 18:02:35 2008
>>> New Revision: 184645
>>> URL: http://svn.freebsd.org/changeset/base/184645
>>>
>>> Log:
>>>   Repeat vmstat header after window.rows instead of a hardcoded 20.
>>>
>>>   Use ioctl() to get the window size in vmstat(8), and force a new
>>>   header to be prepended to the output every time the current window
>>>   size changes.  Change the number of lines before each header to the
>>>   current lines of the terminal when the terminal is resized, so that
>>>   the full terminal length can be used for output lines.
>>>
>>>   Inspired by:	svn change 175562 (same feature for iostat)
>>>   Reviewed by:	ru (who fixed some of my bugs too)
>> Thanks!  This functionality is generally useful and tricky to code in a
>> correct way.  Should we perhaps package it in a library function,  so
>> that all header-printing commands can benefit from it, without
>> repeating the code?
> 
> That's what I thought when I had to write almost the same code a second
> time.  Once is ok, twice is almost ok, but if we find it repeated all
> over the place a library function would definitely be nice :)
> 
> One of the utilities that includes a similar `repeated output' mode that
> I was planning to patch next is procstat(1).  Right now procstat prints
> the header once, and then forgets about it.  When the header scrolls off
> the terminal it's gone for good.
> 
> The code of procstat is quite different that vmstat and iostat though,
> so I'll have to think a bit about the best way to make a library
> function out of the header display code and link all three of them to
> the same code.
> 

And let us not forget netstat and nfsstat (both seem to use a hard-coded 
terminal size).

Let me remark (without actually suggesting that we go down that road) 
that the old-school Unix approach to this problem might be to create a 
separate program that would add a specified header to its input.