bug#53739: 28.0.91; "C-x d" fails when "emacs -Q" starts on NetBSD with plan9/bin on head of PATH

[Van Ly <van.ly@sdf.org>]

On Fri, 4 Feb 2022, Eli Zaretskii wrote:

>
> The problem, as I explained up-thread, seems to be that 'ls' returns a
> non-zero exit status, which insert-directory takes as a sign that the
> directory listing didn't work.

The "9 man intro" page has this paragraph containing the "exit" keyword.

'''
      DIAGNOSTICS
           In Plan 9, a program's exit status is an arbitrary text
           string, while on Unix it is an integer.  Section (1) of this
           manual describes commands as though they exit with string
           statuses.  In fact, exiting with an empty status corresponds
           to exiting with status 0, and exiting with any non-empty
           string corresponds to exiting with status 1.  See exits(3).
'''

>
> So: what does "ls -l" return as exit status when using the plan9
> variant of 'ls'?
>

Starting 'emacs -Q' at the end of this typescript reproduces the problem.

'''
; on GNU/Linux
% echo $SHELL
/usr/bin/zsh
% PATH=/usr/local/plan9/bin:/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin; export PATH
% echo $PATH
/usr/van/.opam/cs3110-2-21fa/bin:/usr/local/plan9/bin:/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin
% which ls
/usr/local/plan9/bin/ls
% ls -l
--rw-r--r-- M 0 van dialout 46 Feb  4 18:22 emacs28
--rw-r--r-- M 0 van dialout 47 Feb  4 18:14 emacs28q
% echo $?
0
% /usr/local/plan9/bin/ls -l
--rw-r--r-- M 0 van dialout 46 Feb  4 18:22 emacs28
--rw-r--r-- M 0 van dialout 47 Feb  4 18:14 emacs28q
% echo $?
0

'''

-- 
vl