---
name: IO::Select
runtime: pp
source: src/native/IO/Select/pp.rs
---
```{index} single: IO::Select; Perl module (pp runtime)
```

# IO::Select

Native implementation of IO::Select

Provides multiplexed I/O via the POSIX select() system call, compatible
with Perl's IO::Select module.

IO::Select objects are blessed hashrefs internally storing:
- `__fds`: an Av mapping fd_number -> stored handle (the original Sv)
- `__count`: integer count of registered handles

# Functions

## new

Constructor. Creates an IO::Select object, optionally pre-populated
with an initial set of handles.

```perl
use IO::Select;
my $sel = IO::Select->new();
my $sel = IO::Select->new($fh1, $fh2);
```

## add

Adds one or more handles to the select set. Returns the number of
handles added.

```perl
$sel->add($fh);
$sel->add(\*STDIN, $sock);
```

## remove

Removes one or more handles from the select set. Returns the number
of handles removed.

```perl
$sel->remove($fh);
```

## count

Returns the number of handles currently registered.

```perl
my $n = $sel->count();
```

## handles

Returns a list of all registered handles.

```perl
my @fhs = $sel->handles();
```

## exists

Checks if a given handle is in the select set. Returns the stored
handle if present, undef otherwise.

```perl
if (defined $sel->exists($fh)) { ... }
```

## bits

Returns the vec-style bitmask string suitable for the 4-argument
`select()` builtin. Returns undef if the set is empty.

```perl
my $bits = $sel->bits();
```

## can_read

Returns a list of handles that are ready for reading within the
given timeout (seconds, fractional allowed).

```perl
my @ready = $sel->can_read(0.5);
```

## can_write

Returns a list of handles that are ready for writing within the
given timeout.

```perl
my @ready = $sel->can_write(1.0);
```

## has_exception

Returns a list of handles that have pending exceptions within the
given timeout.

```perl
my @exc = $sel->has_exception(0);
```

## select

Static/class method. Performs a POSIX `select(2)` across up to three
IO::Select objects (readers, writers, errors) with a timeout.
Returns three arrayrefs of ready handles, or an empty list on timeout.

```perl
my ($r, $w, $e) = IO::Select->select($readers, $writers, $errors, $timeout);
```