1POE::Filter::Grep(3)  User Contributed Perl Documentation POE::Filter::Grep(3)
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NAME

6       POE::Filter::Grep - select or remove items based on simple rules
7

SYNOPSIS

9         #!perl
10
11         use POE qw(
12           Wheel::FollowTail
13           Filter::Line Filter::Grep Filter::Stackable
14         );
15
16         POE::Session->create(
17           inline_states => {
18             _start => sub {
19               my $parse_input_as_lines = POE::Filter::Line->new();
20
21               my $select_sudo_log_lines = POE::Filter::Grep->new(
22                 Put => sub { 1 },
23                 Get => sub {
24                   my $input = shift;
25                   return $input =~ /sudo\[\d+\]/i;
26                 },
27               );
28
29               my $filter_stack = POE::Filter::Stackable->new(
30                 Filters => [
31                   $parse_input_as_lines, # first on get, last on put
32                   $select_sudo_log_lines, # first on put, last on get
33                 ]
34               );
35
36               $_[HEAP]{tailor} = POE::Wheel::FollowTail->new(
37                 Filename => "/var/log/system.log",
38                 InputEvent => "got_log_line",
39                 Filter => $filter_stack,
40               );
41             },
42             got_log_line => sub {
43               print "Log: $_[ARG0]\n";
44             }
45           }
46         );
47
48         POE::Kernel->run();
49         exit;
50

DESCRIPTION

52       POE::Filter::Grep selects or removes items based on simple tests.  It
53       may be used to filter input, output, or both.  This filter is named and
54       modeled after Perl's built-in grep() function.
55
56       POE::Filter::Grep is designed to be combined with other filters through
57       POE::Filter::Stackable.  In the "SYNOPSIS" example, a filter stack is
58       created to parse logs as lines and remove all entries that don't
59       pertain to a sudo process.  (Or if your glass is half full, the stack
60       only selects entries that DO mention sudo.)
61

PUBLIC FILTER METHODS

63       In addition to the usual POE::Filter methods, POE::Filter::Grep also
64       supports the following.
65
66   new
67       new() constructs a new POE::Filter::Grep object.  It must either be
68       called with a single Code parameter, or both a Put and a Get parameter.
69       The values for Code, Put, and Get are code references that, when
70       invoked, return true to select an item or false to reject it.  A Code
71       function will be used for both input and output, while Get and Put
72       functions allow input and output to be filtered in different ways.  The
73       item in question will be passed as the function's sole parameter.
74
75         sub reject_bidoofs {
76           my $pokemon = shift;
77           return 1 if $pokemon ne "bidoof";
78           return;
79         }
80
81         my $gotta_catch_nearly_all = POE::Filter::Grep->new(
82           Code => \&reject_bidoofs,
83         );
84
85       Enforce read-only behavior:
86
87         my $read_only = POE::Filter::Grep->new(
88           Get => sub { 1 },
89           Put => sub { 0 },
90         );
91
92   modify
93       modify() changes a POE::Filter::Grep object's behavior at run-time.  It
94       accepts the same parameters as new(), and it replaces the existing
95       tests with new ones.
96
97         # Don't give away our Dialgas.
98         $gotta_catch_nearly_all->modify(
99           Get => sub { 1 },
100           Put => sub { return shift() ne "dialga" },
101         );
102

SEE ALSO

104       POE::Filter for more information about filters in general.
105
106       POE::Filter::Stackable for more details on stacking filters.
107

BUGS

109       None known.
110

AUTHORS & COPYRIGHTS

112       The Grep filter was contributed by Dieter Pearcey.  Documentation is
113       provided by Rocco Caputo.
114
115       Please see the POE manpage for more information about authors and
116       contributors.
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120perl v5.36.0                      2022-07-22              POE::Filter::Grep(3)
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