Re: PIPESTATUS differs from $? for compound command

[Mike Jonkmans]

On Mon, Dec 09, 2024 at 09:20:54PM +0100, Andreas Schwab wrote:
> On Dez 09 2024, Mike Jonkmans wrote:
> > So, with 'if false; then :; fi', the whole if has 0 as status, due to #1.
> > The last pipeline is the 'false' command. So $PIPESTATUS = 1.
> 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.

> > Both other examples, e.g. 'if false; then :; fi | true',
> > are, for PIPESTATUS purposes, equivalent to: 'true | true'.
> Why is `if false; then :; fi' not equivalent to `true' above?

Not sure why you are asking this.
        $ if false; then :; fi && echo true
        true
Because if statements have status true when the conditions are false
(multiple conditions in the case of elif's),
But the PIPESTATUS refers to the 'false' pipeline:
        $ if false; then :; fi; echo ${PIPESTATUS[*]}
        1
More clearly:
        $ if (exit 42); then :; fi; echo ${PIPESTATUS[*]}
        42

With an explicit pipeline after the if:
        $ if false; then :; fi | true; echo ${PIPESTATUS[*]}
        0 0
In this case the most-recently-executed pipeline is the 'if...fi | true'.

-- 
Regards, Mike Jonkmans