Re: Bad file descriptor with coproc and pipe

[Michal Sojka]

On Wed, Feb 05 2014, Chet Ramey wrote:
> On 2/4/14, 2:34 AM, Michal Sojka wrote:
>
>> Bash Version: 4.2
>> Patch Level: 45
>> Release Status: release
>> 
>> Description:
>>      The following commands fail:
>> 
>>          coproc while true; do echo $RANDOM; done
>>          cat <&${COPROC[0]} | cat
>> 
>>      The resulting error message is:
>> 
>>          bash: ${COPROC[0]}: Bad file descriptor
>
> Bash closes file descriptors associated with coprocs in child processes,
> since they are pipes.  It's even more careful when those child processes
> are part of pipelines.  It's really a bad idea to have pipe file
> descriptors open in multiple processes; that prevents SIGPIPE generation
> and EOF on read when one writer exits.

Thanks for the explanation. Then the bug is that it is not documented:
https://www.gnu.org/software/bash/manual/bashref.html#Coprocesses

Btw. zsh allows using file descriptors this way.

Best regards,
-Michal