Re: Coproc within coproc supported?

[Chet Ramey]

On 11/16/22 2:18 AM, Tadeus Prastowo wrote:
> Hi!
>
> The Bash 4.3.48 that comes shipped with Ubuntu 16.04 does not support
> multiple coprocesses, giving a warning when the second coprocess is
> created ("bash: warning: execute_coproc: coproc [16388:COPROC] still
> exists").

Wow, that's old.

> As documented in the corresponding Bash man page, the section BUGS
> states that "[t]here may be only one active coprocess at a time."

Yes, the shell doesn't try to keep track of more than one coprocess at
a time, and creating a new coproc overwrites the information about any
current one. Any existing shell variables describing previous coprocs
will remain, but the shell won't update them when the coproc exits, for
instance.

> Is it true that the intention of the statement in the man page is that
> at most one coprocess exists for every concurrently running Bash
> process where $$ expands to the same PID?

No. Coprocs are process-based.

--
``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/