Hinrik Örn Sigurðsson > POE-Quickie > POE::Quickie

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Module Version: 0.18   Source  

NAME ^

POE::Quickie - A lazy way to wrap blocking code and programs

SYNOPSIS ^

 use POE::Quickie;

 sub event_handler {
     # the "I'll wait until it's finished" approach, which will block your
     # session until the command has finished
     my ($stdout, $stderr, $exit_status) = quickie('foo.pl');
     print $stdout;

     # the "keep me posted" approach, which will give you each line of output
     # as it is appears
     quickie_run(
         Program     => ['foo.pl', 'bar'],
         StdoutEvent => 'stdout',
         Context     => 'remember this',
     );

     # the "get back to me when it's done" approach, which will notify you
     # of the entire output when the command has finished
     quickie_run(
         Program     => ['foo.pl', 'bar'],
         Context     => 'remember this',
         ResultEvent => 'result',
     );
 }

 sub stdout {
     my ($output, $context) = @_[ARG0, ARG1];
     print "got output: '$output' in the context of '$context'\n";
 }

 sub result {
     my ($pid, $stdout, $stderr, $merged, $status, $context) = @_[ARG0..$#_];
     print "got all this output in the context of '$context':\n";
     print "$_\n" for @$stdout;
 }

DESCRIPTION ^

If you need nonblocking access to an external program, or want to execute some blocking code in a separate process, but you don't want to write a wrapper module or some POE::Wheel::Run boilerplate code, then POE::Quickie can help. You just specify what you're interested in (stdout, stderr, and/or exit code), and POE::Quickie will handle the rest in a sensible way.

It has some convenience features, such as killing processes after a timeout, and storing process-specific context information which will be delivered with every event.

There is also an even lazier API which suspends the execution of your event handler and gives control back to POE while your task is running, the same way LWP::UserAgent::POE does. This is provided by the quickie_* functions which are exported by default.

METHODS ^

new

Constructs a POE::Quickie object. You only need to do this if you want to specify any of the parameters below, since a POE::Quickie object will be constructed automatically when it is needed. The rest of the methods can be called on the object ($object->run()) or as class methods (POE::Quickie->run()). You can safely let the object go out of scope; POE::Quickie will continue to run your processes until they finish.

Takes 3 optional parameters: 'debug', 'default', and 'trace'. These will be passed to the object's POE::Session constructor. See its documentation for details.

run

This method spawns a new child process. It returns its process id.

You can either call it with a single argument (string, arrayref, or coderef), which will used as the 'Program' argument, or you can supply the following key-value pairs:

'Program' (required), will be passed to directly to POE::Wheel::Run's constructor.

'ProgramArgs' (optional), will be passed directly to POE::Wheel::Run's constructor.

'Input' (optional), a string containing the input to the process. This string, if provided, will be sent immediately to the child, and its stdin will then be shut down. Note: no processing will be done on the data before it is sent. For instance, if you are executing a program which expects line-based input, be sure to end your input with a newline.

'StdoutEvent' (optional), the event for delivering lines from the process' STDOUT. If you don't supply this, they will be printed to the main process's STDOUT. To explicitly ignore them, set this to undef.

'StderrEvent' (optional), the event for delivering lines from the process' STDERR. If you don't supply this, they will be printed to the main process' STDERR. To explicitly ignore them, set this to undef.

'ExitEvent' (optional), the event to be called when the process has exited. If you don't supply this, a warning indicating the exit code will be printed if it is nonzero. To explicitly ignore it, set this to undef.

'ResultEvent' (optional), like 'ExitEvent', but it will also contain all the stdout/stderr generated by the child process.

'Context' (optional), a variable which will be sent back to you with every event. If you pass a reference, that same reference will be delivered back to you later (not a copy), so you can update it as you see fit.

'Timeout' (optional), a timeout in seconds after which the process will be forcibly killed if it is still running. There is no timeout by default.

'AltFork' (optional), if true, a new instance of the active Perl interpreter ($^X) will be launched with 'Program' (which must be a string) as the code argument (-e), and the current @INC passed as include arguments (-I). Default is false.

All other arguments will be passed to POE::Wheel::Run's new method. Useful if you want to specify the input/output filters and such.

killall

This kills all processes which POE::Quickie is managing for your session. Takes one optional argument, a signal name (e.g. 'SIGTERM').

processes

Returns a hash reference of all the currently running processes. The key is the process id, and the value is the context variable, if any.

OUTPUT ^

The following events might get sent to your session. The names correspond to the options to run.

StdoutEvent

ARG0: the chunk of STDOUT generated by the process
ARG1: the process id of the child process
ARG2: the context variable, if any

StderrEvent

ARG0: the chunk of STDERR generated by the process
ARG1: the process id of the child process
ARG2: the context variable, if any

ExitEvent

ARG0: the exit code ($?) of the child process
ARG1: the process id of the child process
ARG2: the context variable, if any

ResultEvent

ARG0: the process id of the child process
ARG1: an array of every chunk of stdout generated by the child process
ARG2: an array of every chunk of stderr generated by the child process
ARG3: an array of the interleaved stdout and stderr chunks
ARG4: the exit code ($?) of the child process
ARG5: the context variable, if any

FUNCTIONS ^

quickie_run

Equivalent to POE::Quickie->run(), provided as a convenience.

Blocking functions

The following functions are modeled after the ones provided by Capture::Tiny. They will not return until the executed process has exited. However, run_one_timeslice in POE::Kernel will be called in the meantime, so the rest of your application will continue to run.

They all take the same arguments as the run method, except for the '*Event' and 'Context' arguments.

Note: Since these functions block, you must be careful not to call them in event handlers which were executed with $poe_kernel->call() by other sessions, so you don't hold them up. A simple way to avoid that is to yield() or post() a new event to your session and do it from there.

quickie

Returns 3 values: the stdout, stderr, and exit code ($?) of the child process.

quickie_tee

Returns 3 values: an array of all stdout chunks, an array of all stderr chunks, and the exit code ($?) of the child process. In addition, it will echo the stdout/stderr to your process' stdout/stderr.

quickie_merged

Returns 2 values: an array of interleaved stdout and stderr chunks, and the exit code ($?) of the child process. Beware that stdout and stderr in the merged result are not guaranteed to be properly ordered due to buffering.

quickie_tee_merged

Returns 2 values: an array of interleaved stdout and stderr chunks, and the exit code ($?) of the child process. In addition, it will echo the merged stdout & stderr to your process' stdout. Beware that stdout and stderr in the merged result are not guaranteed to be properly ordered due to buffering.

AUTHOR ^

Hinrik Örn Sigurðsson, hinrik.sig@gmail.com

LICENSE AND COPYRIGHT ^

Copyright 2010-2011 Hinrik Örn Sigurðsson

This program is free software, you can redistribute it and/or modify it under the same terms as Perl itself.

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