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    In version 0.80 or better, you may provide a callback as the last
    argument which is called before on_start, and takes the process object
    as its only argument. For example:

     foreach my $i (1..10)
     {
       $ipc->run($prog, @args, \$stdin, sub {
         my($proc) = @_;
         $proc->user({ iteration => $i });
       });
     }

    This is useful for making data accessible to $ipc object's callbacks
    that may be out of scope otherwise.

CAVEATS

    Some AnyEvent implementations may not work properly with the method
    used by AnyEvent::Open3::Simple to wait for the child process to
    terminate. See "CHILD PROCESS WATCHERS" in AnyEvent for details.

    This module uses an idle watcher instead of a child watcher to detect
    program termination on Microsoft Windows (but not Cygwin). This is
    because the child watchers are unsupported by AnyEvent on Windows. The
    idle watcher implementation seems to pass the test suite, but there may
    be some traps for the unwary. There may be other platforms or event
    loops where this is the appropriate choice, and you can use the
    ANYEVENT_OPEN3_SIMPLE environment variable or the implementation
    attribute to force it use an idle watcher instead. Patches for
    detecting environments where idle watchers should be used are welcome
    and encouraged.

    As of version 0.85, this module works on Windows with
    AnyEvent::Impl::EV, AnyEvent::Impl::Event and AnyEvent::Impl::Perl
    (possibly others), although in the past they have either not worked or
    had limitations placed on them. Because the author of AnyEvent does not
    hold the native Windows port of Perl in high regard: problems such as
    this may pop up again in the future and may not be addressed, and may
    be out of the control of the author of this module.

    Performance for the idle watcher implementation on native Windows
    (non-Cygwin) is almost certainly suboptimal, but the author of this
    module uses it and finds it useful despite this.

    Writing to a subprocesses stdin with
    AnyEvent::Open3::Simple::Process#print or
    AnyEvent::Open3::Simple::Process#say is unsupported on Microsoft
    Windows (it does work under Cygwin though).

    There are some traps for the unwary relating to buffers and deadlocks,
    IPC::Open3 is recommended reading.

    If you register a call back for on_exit, but not on_error then use a
    condition variable to wait for the process to complete as in this:

     my $cv = AnyEvent->condvar;
     my $ipc = AnyEvent::Open3::Simple->new(
       on_exit => sub { $cv->send },
     );
     $ipc->run('command_not_found');
     $cv->recv;

    You might be waiting forever if there is an error starting the process
    (if for example you give it a bad command). To handle this situation
    you might use croak on the condition variable in the event of error:

     my $cv = AnyEvent->condvar;
     my $ipc = AnyEvent::Open3::Simple->new(
       on_exit => sub { $cv->send },
       on_error => sub {
         my $error = shift;
         $cv->croak($error);
       },
     );
     $ipc->run('command_not_found');
     $cv->recv;

    This will cause the recv to die, printing a useful diagnostic if the
    exception isn't caught somewhere else.

SEE ALSO

    AnyEvent::Open3::Simple::Process

      Represents a process being run by this module, typically passed into
      the callbacks.

    AnyEvent::Subprocess

      Alternative to this module.

    AnyEvent::Run

      Alternative to this module.

AUTHOR

    Author: Graham Ollis <plicease@cpan.org>

    Contributors:

    Stephen R. Scaffidi

    Scott Wiersdorf

    Graham Knop (HAARG)

COPYRIGHT AND LICENSE

    This software is copyright (c) 2012-2022 by Graham Ollis.

    This is free software; you can redistribute it and/or modify it under
    the same terms as the Perl 5 programming language system itself.