Re: PIPESTATUS differs from $? for compound command

[Mike Jonkmans]

On Tue, Dec 10, 2024 at 09:28:31AM +0100, Ulrich Müller wrote:
> >>>>> On Mon, 09 Dec 2024, Mike Jonkmans wrote:
> 
> >> Why is `if false; then :; fi' not a pipeline?  It is a command, and the
> >> components of a pipeline are commands.
> 
> > It is a pipeline indeed, but not the last
> > (doc says: most-recently-executed).
> > The last is the 'false' simple command/pipeline.
> 
> Then what about these?
> 
> $ true; case a in esac
> $ echo "ret = $?, status = ${PIPESTATUS[*]}"
> ret = 0, status = 0
> 
> $ false; case a in esac
> $ echo "ret = $?, status = ${PIPESTATUS[*]}"
> ret = 0, status = 1
> 
> "case a in esac" is a one-command pipeline, and certainly it is executed
> after "false". So it should qualify as "the most-recently-executed
> foreground pipeline (which may contain only a single command)".

It is indeed confusing.


Also compare:
        $ if false; then echo foo; fi
        $ echo "ret = $?, status = ${PIPESTATUS[*]}"
        ret = 0, status = 1
To:
        $ if ! :; then echo foo; fi
        $ echo "ret = $?, status = ${PIPESTATUS[*]}"
        ret = 0, status = 0

The '! :' is a pipeline with status = 1.
Yet it is not reflected in PIPESTATUS.

I think that 'most-recently-executed pipeline' needs some clarification.

Seemingly a compound command is not considered a pipeline,
when there is no simple command ran. 
Moreover, the '!'-part of a pipeline is not influencing PIPESTATUS.

-- 
Regards, Mike Jonkmans