Re: read command sometimes misses newline on timeout

[alex xmb sw ratchev]

there is a case , u [[ $readreply ]] after read

On Monday, October 7, 2024, Thomas Oettli via Bug reports for the GNU
Bourne Again SHell <bug-bash@gnu.org> wrote:

> I agree with you, but it should never happen that read returns timeout,
> also returns the full line and has already read the newline character.
> If that happens, there is no way for the script to decide what to do.
> Please see the provided test script, it showcases the error.
>
> If I did a mistake there, I would gladly change it. But I currently don't
> see any way how to handle this properly from the script side.
>
> Please also see the answer from Martin D Kealey, I think he is on to
> something:
> https://lists.gnu.org/archive/html/bug-bash/2024-10/msg00007.html
>
>
>
>
> On 10/4/24 8:18 AM, Thomas Oettli via Bug reports for the GNU Bourne Again
> SHell wrote:
>
> > Bash Version: 5.2
> > Patch Level: 26
> > Release Status: release
> >
> > Description:
> > I have tried to write a bash script that asynchronously reads from a
> pipe (line by line) with the help of "read -t".
> > If the timeout occurs in just the right moment, read returns the full
> line, but the return code says timeout (rc > 128).
>
> If the read command times out, it always returns > 128, so if you have a
> return code in that range, you can assume read timed out and react
> accordingly.
>
> > Therefor it is not possible to know if a full line was returned or not.
>
> When read times out, it always returns what it read before the timeout in
> the buffer, so you don't lose any data. Whether or not that's a `full line'
> is up to timing, and it's up to the script to decide how to cope with it.
>
> --
> ``The lyf so short, the craft so long to lerne.'' - Chaucer
> ``Ars longa, vita brevis'' - Hippocrates
> Chet Ramey, UTech, CWRU chet@case.edu http://tiswww.cwru.edu/~chet/
>
>