Re: $? in a simple command with no command name

[Harald van Dijk via austin-group-l at The Open Group]

On 01/09/2021 18:48, Robert Elz via austin-group-l at The Open Group wrote:
     Date:        Wed, 1 Sep 2021 16:38:00 +0300
     From:        "=?UTF-8?B?T8SfdXo=?= via austin-group-l at The Open Group" 
<austin-group-l@opengroup.org>
     Message-ID:  
<cah7i3lpfk0tfxwpqny3ma6hzmptsqvsysq5nfzfxetr7yeq...@mail.gmail.com>
   | true
   | a=$? b=`exit 1` b=$? >`echo /dev/null; exit 2`
   | echo $? $a $b

   | Now, I wonder, what did I miss?

That $? (the exit status) is defined only when a command completes.
What it is in the middle of a command execution isn't specified.

$? is defined as "Expands to the decimal exit status of the most recent 
pipeline (see Pipelines)." During the a=$? and b=$? assignments, the 
most recent pipeline in that shell execution environment was 'true' at 
line 1. Is there any statement that overrides the general definition to 
explicitly make this unspecified? If not, the general definition applies 
and $? must expand to 0 both times it appears on line 2.

Cheers,
Harald van Dijk