NAME

    AnyEvent::Open3::Simple - Interface to open3 under AnyEvent

VERSION

    version 0.85

SYNOPSIS

     use 5.010;
     use AnyEvent;
     use AnyEvent::Open3::Simple;
     
     my $done = AnyEvent->condvar;
     
     my $ipc = AnyEvent::Open3::Simple->new(
       on_start => sub {
         my $proc = shift;       # isa AnyEvent::Open3::Simple::Process
         my $program = shift;    # string
         my @args = @_;          # list of arguments
         say 'child PID: ', $proc->pid;
       },
       on_stdout => sub { 
         my $proc = shift;       # isa AnyEvent::Open3::Simple::Process
         my $line = shift;       # string
         say 'out: ', $string;
       },
       on_stderr => sub {
         my $proc = shift;       # isa AnyEvent::Open3::Simple::Process
         my $line = shift;       # string
         say 'err: ', $line;
       },
       on_exit   => sub {
         my $proc = shift;       # isa AnyEvent::Open3::Simple::Process
         my $exit_value = shift; # integer
         my $signal = shift;     # integer
         say 'exit value: ', $exit_value;
         say 'signal:     ', $signal;
         $done->send;
       },
       on_error => sub {
         my $error = shift;      # the exception thrown by IPC::Open3::open3
         my $program = shift;    # string
         my @args = @_;          # list of arguments
         warn "error: $error";
         $done->send;
       },
     );
     
     $ipc->run('echo', 'hello there');
     $done->recv;

DESCRIPTION

    This module provides an interface to open3 while running under AnyEvent
    that delivers data from stdout and stderr as lines are written by the
    subprocess. The interface is reminiscent of IPC::Open3::Simple,
    although this module does provides a somewhat different API, so it
    cannot be used a drop in replacement for that module.

    There are already a number of interfaces for interacting with
    subprocesses in the context of AnyEvent, but this one is the most
    convenient for my usage. Note the modules listed in the SEE ALSO
    section below for other interfaces that may be more or less
    appropriate.

CONSTRUCTOR

    Constructor takes a hash or hashref of event callbacks and attributes.
    Event callbacks have an on_ prefix, attributes do not.

 ATTRIBUTES

      * implementation

      The implementation to use for detecting process termination. This
      should be one of child or idle. On all platforms except for Microsoft
      Windows (but not Cygwin) the default is child.

      You can change the default by setting the ANYEVENT_OPEN3_SIMPLE
      environment variable, like this:

       % export ANYEVENT_OPEN3_SIMPLE=idle

      AnyEvent::Open3::Simple::Process#print

      AnyEvent::Open3::Simple::Process#say

      AnyEvent::Open3::Simple#run

 EVENTS

    These events will be triggered by the subprocess when the run method is
    called. Each event callback (except on_error) gets passed in an
    instance of AnyEvent::Open3::Simple::Process as its first argument
    which can be used to get the PID of the subprocess, or to write to it.
    on_error does not get a process object because it indicates an error in
    the creation of the process.

    Not all of these events will fire depending on the execution of the
    child process. In the very least exactly one of on_start or on_error
    will be called.

      * on_start ($proc, $program, @arguments)

      Called after the process is created, but before the run method
      returns (that is, it does not wait to re-enter the event loop first).

      In versions 0.78 and better, this event also gets the program name
      and arguments passed into the run method.

      * on_error ($error, $program, @arguments)

      Called when there is an execution error, for example, if you ask to
      run a program that does not exist. No process is passed in because
      the process failed to create. The error passed in is the error thrown
      by IPC::Open3 (typically a string which begins with "open3: ...").

      In some environments open3 is unable to detect exec errors in the
      child, so you may not be able to rely on this event. It does seem to
      work consistently on Perl 5.14 or better though.

      Different environments have different ways of handling it when you
      ask to run a program that doesn't exist. On Linux and Cygwin, this
      will raise an on_error event, on MSWin32 it will not trigger a
      on_error and instead cause a normal exit with a exit value of 1.

      In versions 0.77 and better, this event also gets the program name
      and arguments passed into the run method.

      * on_stdout ($proc, $line)

      Called on every line printed to stdout by the child process.

      * on_stderr ($proc, $line)

      Called on every line printed to stderr by the child process.

      * on_exit ($proc, $exit_value, $signal)

      Called when the processes completes, either because it called exit,
      or if it was killed by a signal.

      * on_success ($proc)

      Called when the process returns zero exit value and is not terminated
      by a signal.

      * on_signal ($proc, $signal)

      Called when the processes is terminated by a signal.

      * on_fail ($proc, $exit_value)

      Called when the process returns a non-zero exit value.

METHODS

 run

     $ipc->run($program, @arguments);
     $ipc->run($program, @arguments, \$stdin);             # (version 0.76)
     $ipc->run($program, @arguments, \@stdin);             # (version 0.76)
     $ipc->run($program, @arguments, sub {...});           # (version 0.80)
     $ipc->run($program, @arguments, \$stdin, sub {...});  # (version 0.80)
     $ipc->run($program, @arguments, \@stdin, sub {...});  # (version 0.80)

    Start the given program with the given arguments. Returns immediately.
    Any events that have been specified in the constructor (except for
    on_start) will not be called until the process re-enters the event
    loop.

    You may optionally provide the full content of standard input as a
    string reference or list reference as the last argument (or second to
    last if you are providing a callback below). If provided as a list
    reference, it will be joined by new lines in whatever format is native
    to your Perl. Currently on (non cygwin) Windows (Strawberry,
    ActiveState) this is the only way to provide standard input to the
    subprocess.

    Do not mix the use of passing standard input to run and
    AnyEvent::Open3::Simple::Process#print or
    AnyEvent::Open3::Simple::Process#say, otherwise bad things may happen.

    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::Subprocess, AnyEvent::Util, AnyEvent::Run.

AUTHOR

    Author: Graham Ollis <plicease@cpan.org>

    Contributors:

    Stephen R. Scaffidi

    Scott Wiersdorf

COPYRIGHT AND LICENSE

    This software is copyright (c) 2012 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.

