Re: multi-threaded compiling

[Robert Elz]

This whole discussuon has been a total mess.

First the original message didn't give nearly enough info.
That might have been in the attachment, but no-one should be
expecting people to do any needless work when you're asking
for (free) assistance - if you want help you need to make
it as easy as possible for people to do that.

Second, a very common issue with people having problems, is
when they have a problem to solve, they work out how they think
they should do that, and then have difficulty making one
of the steps work.  At that point they ask how to do that
thing, which might sometimes be very complex, even impossible.
If the initial problem had been stated, along with the
solution proposed, leading to the issue that's hard, then
instead of (perhaps) wasting needless time dreaming up
possible solutions to difficult problems, someone might
just point out a much simpler method to solve the original
problem, making finding a solution to the difficult issue moot.

Second, the replies here have mostly been hopeless, with
just a couple addressing real issues.

Many of the initial replies totally missed that the OP
said that the bash script in 'one' worked, and there
was this long thread suggesting other ways to do it.
Waste if everyone's time (even if the advice not to
use SECONDS was probably useful).

There is however no blanket rule that vars in upper case are
reserved for the shell - posix contains a list of var
names scripts should avoid using (unless they want some
particular feature supported by a particular shell they
are using - SECONDS & RANDOM are on that list).   Anything
else is (or should be) OK to use.

The issue with 'one' was that the same code did not work on
the command line, or in a makefile.

Chet explained the command line problem:

    Date:        Mon, 11 Mar 2024 17:25:57 -0400
    From:        Chet Ramey <chet.ramey@case.edu>
    Message-ID:  <322e10a6-3808-49be-aa9d-a1d367a90572@case.edu>

  | OK, here's the longer answer. When the shell is interactive, and job
  | control is enabled, the shell prints job completion notifications to
  | stdout at command boundaries.

which is, IMO, yet another bogus bash misfeature.  That should
happen, with the effect described, but only when PS1 is about
to be printed - precisely so commands like the one described
will work.   Sigh.

There aren't many complaints about this misfeature of bash,
as almost no-one writes interactive command lines where it makes
a difference.   That doesn't mean they should not be able to.


For the problem using make, it was suggested to explicity set
the SHELL to use in the makefile, which is good advice when
using shell specific features, as is being done here.

But the real problem is almost certainly that the Makefile
is attempting to pass scripts containing '$' chars to the
shell.  '$' is interpreted by make, to send a '$' to the
shell, it must be written as '$$'.


For problem 'two', Greg (I think it was) diagnosed the
issue with var expansions, and field splitting - but if
that was unknown to the OP then that OP has no business
attempting to write any shell script (with any kind of
variable) - get an introductory shell programming text
and learn how it works - at least the basics.  Don't
just guess or attempt to copy other scripts, you'll fail.

kre