One method is to keep pipes open to the children - if you have a pipe which the parent reads and the child writes, you can send your dots (valid progess indicators :) down the pipe. You then remove file locking problems (which you have with writing dots to a file). You end up with a parent with a whole bunch of pipes - just do a select() on these, and you'll get woken up whenever there's anything to read from them.

Pipes were pretty much invented for this - they survive fork (i.e., both child and parent can still see it!). Pipes rock :) Programming Perl has some other good examples of IPC - shared memory, sockets, etc., but all that's a bit overboard for what you want. The usual pipe way is:

pipe(READHANDLE, WRITEHANDLE);
my $result = fork();
if ($result>0) {
    # child process, we write to the pipe
} else {
    # parent process, or error - might want to check before
    # we try to read from pipe :))
}
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If you want more than one child, just keep the handles in an array so you don't lose them, and do a select() in the parent when all the children are active.

Oh, and beware of buffering - probably best to turn that off when debugging :)

How about using the open call which forks a child and attaches the child's STDOUT to a file handle? From there, it is a matter of having the children printing to STDOUT and the parent using select() to check for waiting input.

See perldoc perlipc under the "Safe Pipe Opens" section for the syntax a a discussion of how to use the open() call effectively.

mikfire

By the way, this is the complaint I have with that bad child-reaper meme that uses a wait inside a SIGCHLD handler. Multiple SIGCHLDs will be stacked as one, and therefore some kids will be missed and zombified at random.

-- Randal L. Schwartz, Perl hacker

use IO::Handle;
if ($pid = open(CHILD1, "-|")) {

  here you can read fom STDIN that what your child will tell you,
  but I don't know if this methode works with multiple childs.
}
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But if you only need to know when the kids died, just pollwaitpid periodically to find out if any more kids exited.

- instead of a signal for every message, send one for every 10th or some pre-set number. Better would be to get each child to signal on every 10% complete of whatever their task was. This would still cause problems if their tasks were very small though, and it certainly wouldn't ensure that no signals were lost.

- Try a whole different approach using IPC::Shareable, and have a look at this thread which may help.

--
I'd like to be able to assign to an luser

ChOas