Re: waiting for process substitutions

[Zachary Santer]

On Tue, Jul 9, 2024 at 6:12 AM Zachary Santer <zsanter@gmail.com> wrote:
>
> command-1 | tee >( command-2 ) >( command-3 ) >( command-4 )
> wait
>
> The workaround for this not working would of course be named pipes,
> which is somewhat less trivial.

> Bash is already tracking the pids for all child processes not waited
> on, internally. So I imagine it wouldn't be too much work to make that
> information available to the script it's running. Obviously, this is
> moving beyond "make the existing features make more sense," but an
> array of pids of all child processes not waited on would at least
> allow the user to derive pids of what just got forked from a
> comparison of that array before and after a command including multiple
> procsubs. An array variable like what Alex is suggesting, something
> listing all pids resulting from the last pipeline to fork any child
> process in the current shell environment, would be a solution to the
> matter at hand here.
>
> Maybe a single middle-ground array variable, listing the pids of all
> child processes forked (and not waited on) since the last time the
> array variable was referenced, would be more easily implemented. You
> would just have to save the contents of the array variable in a
> variable of your own each time you reference it, if you want to keep
> track of that stuff. Not unreasonable, considering that you already
> have to do that with $!, at least before each time you fork another
> child process.

On the other hand, do funsubs give us the answer here?

shopt -s lastpipe
declare -a pid=()
command-1 | tee >( command-2 ) ${ pid+=( "${!}" ); } >( command-3 ) ${
pid+=( "${!}" ); } >( command-4 ) ${ pid+=( "${!}" ); }
wait -- "${pid[@]}"

That looks obnoxious, and I should probably get Cygwin going and build
bash-5.3-alpha for myself instead of just asking if this would work
and is sane. That could take me 'til the weekend, though.

On Tue, Jul 9, 2024 at 6:12 AM Zachary Santer <zsanter@gmail.com> wrote:
>
> On Fri, Jul 5, 2024 at 3:16 PM Chet Ramey <chet.ramey@case.edu> wrote:
> >
> > On 7/3/24 8:40 PM, Zachary Santer wrote:
> > >
> > > Hypothetically, it could work like this:
> > > {
> > >    commands
> > > } {fd[0]}< <( command-1 )  {fd[1]}< <( command-2 ) {fd[2]}< <( command-3 )
> > > But then again, *I can't get the pids for the processes if I do it this 
> > > way*.

declare -a pid=()
{
  commands
} {fd[0]}< <( command-1 )  ${ pid+=( "${!}" ); } {fd[1]}< <( command-2
) ${ pid+=( "${!}" ); } {fd[2]}< <( command-3 ) ${ pid+=( "${!}" ); }

Do things start breaking?