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.IX Title "Select 3pm"
.TH Select 3pm 2024-01-11 "perl v5.38.2" "User Contributed Perl Documentation"
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.SH NAME
Coro::Select \- a (slow but coro\-aware) replacement for CORE::select
.SH SYNOPSIS
.IX Header "SYNOPSIS"
.Vb 3
\& use Coro::Select;          # replace select globally (be careful, see below)
\& use Core::Select \*(Aqselect\*(Aq; # only in this module
\& use Coro::Select ();       # use Coro::Select::select
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.SH DESCRIPTION
.IX Header "DESCRIPTION"
This module tries to create a fully working replacement for perl's
\&\f(CW\*(C`select\*(C'\fR built-in, using \f(CW\*(C`AnyEvent\*(C'\fR watchers to do the job, so other
threads can run in parallel to any select user. As many libraries that
only have a blocking API do not use global variables and often use select
(or IO::Select), this effectively makes most such libraries "somewhat"
non-blocking w.r.t. other threads.
.PP
This implementation works fastest when only very few bits are set in the
fd set(s).
.PP
To be effective globally, this module must be \f(CW\*(C`use\*(C'\fR'd before any other
module that uses \f(CW\*(C`select\*(C'\fR, so it should generally be the first module
\&\f(CW\*(C`use\*(C'\fR'd in the main program. Note that overriding \f(CW\*(C`select\*(C'\fR globally
might actually cause problems, as some \f(CW\*(C`AnyEvent\*(C'\fR backends use \f(CW\*(C`select\*(C'\fR
themselves, and asking AnyEvent to use Coro::Select, which in turn asks
AnyEvent will not quite work.
.PP
You can also invoke it from the commandline as \f(CW\*(C`perl \-MCoro::Select\*(C'\fR.
.PP
To override select only for a single module (e.g. \f(CW\*(C`Net::DBus::Reactor\*(C'\fR),
use a code fragment like this to load it:
.PP
.Vb 5
\&   {
\&      package Net::DBus::Reactor;
\&      use Coro::Select qw(select);
\&      use Net::DBus::Reactor;
\&   }
.Ve
.PP
Some modules (notably POE::Loop::Select) directly call
\&\f(CW\*(C`CORE::select\*(C'\fR. For these modules, we need to patch the opcode table by
sandwiching it between calls to \f(CW\*(C`Coro::Select::patch_pp_sselect\*(C'\fR and
\&\f(CW\*(C`Coro::Select::unpatch_pp_sselect\*(C'\fR:
.PP
.Vb 6
\& BEGIN {
\&    use Coro::Select ();
\&    Coro::Select::patch_pp_sselect;
\&    require evil_poe_module_using_CORE::SELECT;
\&    Coro::Select::unpatch_pp_sselect;
\& }
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.SH BUGS
.IX Header "BUGS"
For performance reasons, Coro::Select's select function might not
properly detect bad file descriptors (but relying on EBADF is inherently
non-portable).
.SH "SEE ALSO"
.IX Header "SEE ALSO"
Coro::LWP.
.SH AUTHOR/SUPPORT/CONTACT
.IX Header "AUTHOR/SUPPORT/CONTACT"
.Vb 2
\&   Marc A. Lehmann <schmorp@schmorp.de>
\&   http://software.schmorp.de/pkg/Coro.html
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