a survey

% date
Sat Sep 21 20:19:15 UTC 2024

% uname -mprs
NetBSD 10.0 amd64 x86_64

% top -b --pid $$ | tail -3
  PID USERNAME PRI NICE   SIZE   RES STATE       TIME   WCPU    CPU COMMAND
22700 jutty   85    0    25M 2632K pause/3     0:00  0.00%  0.00% zsh

% echo $SHELL
/usr/pkg/bin/zsh

% $SHELL --version
zsh 5.9 (x86_64--netbsd)

% which ksh
/bin/ksh

% ksh --version
ksh: ksh: --: unknown option
ksh: 

% man ksh
% ksh -c 'echo $KSH_VERSION'
@(#)PD KSH v5.2.14 99/07/13.2

% which sh
/bin/sh

% man sh

% echo 'echo $NETBSD_SHELL' | sh
20220122 BUILD:20240328083333Z

% man sh | grep appeared -A 5
man: Formatting manual page...
     A sh command appeared in Version 1 AT&T UNIX.  It was replaced in
     Version 7 AT&T UNIX with a version that introduced the basis of the
     current syntax.  That was, however, unmaintainable so we wrote this one.
     This NetBSD sh is a much modified descendant of the ash shell written by
     Ken Almquist.