Re: 'wait' in command group in pipeline fails to recognize child process

[Martin Jambon]

On 6/22/21 5:00 PM, Lawrence Velázquez wrote:
> Maybe something like this would get the point across:
>
>         ($$) Expands to the process ID of the shell.  In a subshell,
>              it expands to the value that $$ has in the invoking shell.

It's better. However, the reader is still left wondering what "the 
shell" is referring to in first sentence.

Here's my next suggestion, which borrows some language from the 
documentation for BASHPID:

  ($$) Expands to the ID of the process that initialized Bash. The 
value of $$ is inherited in subshells, such as pipelines, regardless of 
their own process ID. See also the Bash variable BASHPID.

For reference, the documentation for 'BASHPID' is this:

  Expands to the process ID of the current Bash process. This differs 
from $$ under certain circumstances, such as subshells that do not 
require Bash to be re-initialized. Assignments to BASHPID have no 
effect. If BASHPID is unset, it loses its special properties, even if it 
is subsequently reset.