Re: LINENO is affected by sync

[David Collier]

greg - I'm sorry - I assume there is a proper place for me to post
follow-up info, can you let me know where it is?

I could try for a short script, but this thing is a bit like herding eels.
I narrowed it down to a single line containing 'sync' - but as you say
that's clearly impossible.
And to my embarrassment the bug remains unchanged when I comment-out
the word sync.

!!!!!!!!!!!!!!!Here is a code segment ( I have removed a few == signs so it
fits across my screen. ):

echo "================ At this point \$LINENO has correctly counted about
2800 lines=========================test @ 2838 $LINENO"
echo "=== Something makes bash lose a few counts from \$LINENO - in this
case about nine - no idea how to fix it. ==="

if ! filesOrSubdirsPresent "${rootOfDummyFsToInstallAPADN}/usr/sbin/*"
then :
    if ${G_verbose} ; then echo "Skipping  ${targetAPARN} - nothing found";
fi
else :
    echo "Installing: ${targetAPARN}*"

    # Do we really want the '-p' option here??? - it corrupts ownership of
directories!
    ( cp -dpR "${rootOfDummyFsToInstallAPADN}"/usr/sbin/* ${cpDestFlag}
 "${targetAPARN}" )

    # Not sure we can know that there are no .sh or .pl scripts already
there but with execute off.
    # but we install so many we can't go round naming them one-by-one.
    #
    setExecutabilityOfScriptsInEntireBranch  "${targetAPARN}"   # All of
our scripts in /usr/sbin do have .sh extensions.
echo
"===========================================================================================test
@ +16  $LINENO"
    sync

fi
echo
"==========================================================================================test
@ +20  $LINENO"

!!!!!!!!!!!!!!!here is the output - it is identical if I put a pound
character in front of 'sync':

========================= At this point $LINENO has correctly counted about
2800 lines=========================test @ 2838 2838
=== Something makes bash lose a few counts from $LINENO - in this case
about nine - no idea how to fix it. ===
Installing: /usr/sbin/*
===============================================================================================test
@ +16  2854
===============================================================================================test
@ +20  2849

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

As you can see, four lines further on, and LINENO has gone down by 5 -
making it 9 too small
I would fiddle around with line endings, but since it literally cogs
backwards I don't think it's going to be anything simple like that.
This happens again at intervals - wrong by different small numbers I think
- weirdly enough the next time it happens is also near a 'sync' operation -
which is what misled me.

Anyway - apologies for the red herring any suggestion welcome.
Do tell me if there is a proper place to put this info.


On Wed, Sep 1, 2021 at 4:01 PM Greg Wooledge <greg@wooledge.org> wrote:

> On Wed, Sep 01, 2021 at 10:36:21AM +0100, David Collier wrote:
> > Version:
> >
> >     GNU bash, version 5.0.3(1)-release (arm-unknown-linux-gnueabihf)
> >
> > Raspberry Pi using Raspbian.
> >
> > Installed from repo?
> >
> > LINENO goes backwards when run sync
> >
> > echo "================== At this point \$LINENO has correctly counted
> about
> > 2800 lines=========================test @ 2832 $LINENO"
> > echo "=== Running 'sync' makes bash lose a few counts from \$LINENO - in
> > this case about ten - no idea how to fix it. ==="
> >     sync
> > echo
> >
> "========================================================================================test
> > @ 2835 $LINENO"
>
> There is no plausible reason an external command (sync or any other
> external command) would be able to change the value of LINENO, which is
> an internal shell variable.
>
> Can you post a brief but complete script which demonstrates the problem?
> I suspect whatever issue you're seeing is caused by something else, not
> by the "sync" command.
>