1IO::Select(3pm)        Perl Programmers Reference Guide        IO::Select(3pm)
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NAME

6       IO::Select - OO interface to the select system call
7

SYNOPSIS

9           use IO::Select;
10
11           $s = IO::Select->new();
12
13           $s->add(\*STDIN);
14           $s->add($some_handle);
15
16           @ready = $s->can_read($timeout);
17
18           @ready = IO::Select->new(@handles)->can_read(0);
19

DESCRIPTION

21       The "IO::Select" package implements an object approach to the system
22       "select" function call. It allows the user to see what IO handles, see
23       IO::Handle, are ready for reading, writing or have an exception
24       pending.
25

CONSTRUCTOR

27       new ( [ HANDLES ] )
28           The constructor creates a new object and optionally initialises it
29           with a set of handles.
30

METHODS

32       add ( HANDLES )
33           Add the list of handles to the "IO::Select" object. It is these
34           values that will be returned when an event occurs. "IO::Select"
35           keeps these values in a cache which is indexed by the "fileno" of
36           the handle, so if more than one handle with the same "fileno" is
37           specified then only the last one is cached.
38
39           Each handle can be an "IO::Handle" object, an integer or an array
40           reference where the first element is an "IO::Handle" or an integer.
41
42       remove ( HANDLES )
43           Remove all the given handles from the object. This method also
44           works by the "fileno" of the handles. So the exact handles that
45           were added need not be passed, just handles that have an equivalent
46           "fileno"
47
48       exists ( HANDLE )
49           Returns a true value (actually the handle itself) if it is present.
50           Returns undef otherwise.
51
52       handles
53           Return an array of all registered handles.
54
55       can_read ( [ TIMEOUT ] )
56           Return an array of handles that are ready for reading. "TIMEOUT" is
57           the maximum amount of time to wait before returning an empty list,
58           in seconds, possibly fractional. If "TIMEOUT" is not given and any
59           handles are registered then the call will block.
60
61       can_write ( [ TIMEOUT ] )
62           Same as "can_read" except check for handles that can be written to.
63
64       has_exception ( [ TIMEOUT ] )
65           Same as "can_read" except check for handles that have an exception
66           condition, for example pending out-of-band data.
67
68       count ()
69           Returns the number of handles that the object will check for when
70           one of the "can_" methods is called or the object is passed to the
71           "select" static method.
72
73       bits()
74           Return the bit string suitable as argument to the core select()
75           call.
76
77       select ( READ, WRITE, EXCEPTION [, TIMEOUT ] )
78           "select" is a static method, that is you call it with the package
79           name like "new". "READ", "WRITE" and "EXCEPTION" are either "undef"
80           or "IO::Select" objects. "TIMEOUT" is optional and has the same
81           effect as for the core select call.
82
83           The result will be an array of 3 elements, each a reference to an
84           array which will hold the handles that are ready for reading,
85           writing and have exceptions respectively. Upon error an empty list
86           is returned.
87

EXAMPLE

89       Here is a short example which shows how "IO::Select" could be used to
90       write a server which communicates with several sockets while also
91       listening for more connections on a listen socket
92
93           use IO::Select;
94           use IO::Socket;
95
96           $lsn = IO::Socket::INET->new(Listen => 1, LocalPort => 8080);
97           $sel = IO::Select->new( $lsn );
98
99           while(@ready = $sel->can_read) {
100               foreach $fh (@ready) {
101                   if($fh == $lsn) {
102                       # Create a new socket
103                       $new = $lsn->accept;
104                       $sel->add($new);
105                   }
106                   else {
107                       # Process socket
108
109                       # Maybe we have finished with the socket
110                       $sel->remove($fh);
111                       $fh->close;
112                   }
113               }
114           }
115

AUTHOR

117       Graham Barr. Currently maintained by the Perl Porters.  Please report
118       all bugs to <perlbug@perl.org>.
119
121       Copyright (c) 1997-8 Graham Barr <gbarr@pobox.com>. All rights
122       reserved.  This program is free software; you can redistribute it
123       and/or modify it under the same terms as Perl itself.
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127perl v5.26.3                      2018-03-01                   IO::Select(3pm)
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