Re: read command sometimes misses newline on timeout

[Chet Ramey]

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/

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