1MCE::Signal(3)        User Contributed Perl Documentation       MCE::Signal(3)
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NAME

6       MCE::Signal - Temporary directory creation/cleanup and signal handling
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VERSION

9       This document describes MCE::Signal version 1.866
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SYNOPSIS

12        ## Creates tmp_dir under $ENV{TEMP} if defined, otherwise /tmp.
13
14        use MCE::Signal;
15
16        ## Attempts to create tmp_dir under /dev/shm if writable.
17
18        use MCE::Signal qw( -use_dev_shm );
19
20        ## Keeps tmp_dir after the script terminates.
21
22        use MCE::Signal qw( -keep_tmp_dir );
23        use MCE::Signal qw( -use_dev_shm -keep_tmp_dir );
24
25        ## MCE loads MCE::Signal by default when not present.
26        ## Therefore, load MCE::Signal first for options to take effect.
27
28        use MCE::Signal qw( -keep_tmp_dir -use_dev_shm );
29        use MCE;
30

DESCRIPTION

32       This package configures $SIG{ HUP, INT, PIPE, QUIT, and TERM } to point
33       to stop_and_exit and creates a temporary directory. The main process
34       and workers receiving said signals call stop_and_exit, which signals
35       all workers to terminate, removes the temporary directory unless
36       -keep_tmp_dir is specified, and terminates itself.
37
38       The location of the temp directory resides under $ENV{TEMP} if defined,
39       otherwise /dev/shm if writeable and -use_dev_shm is specified, or /tmp.
40       On Windows, the temp directory is made under $ENV{TEMP}/Perl-MCE/.
41
42       As of MCE 1.405, MCE::Signal no longer calls setpgrp by default. Pass
43       the -setpgrp option to MCE::Signal to call setpgrp.
44
45        ## Running MCE through Daemon::Control requires setpgrp to be called
46        ## for MCE releases 1.511 and below.
47
48        use MCE::Signal qw(-setpgrp);   ## Not necessary for MCE 1.512 and above
49        use MCE;
50
51       The following are available options and their meanings.
52
53        -keep_tmp_dir     - The temporary directory is not removed during exiting
54                            A message is displayed with the location afterwards
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56        -use_dev_shm      - Create the temporary directory under /dev/shm
57        -no_kill9         - Do not kill -9 after receiving a signal to terminate
58
59        -setpgrp          - Calls setpgrp to set the process group for the process
60                            This option ensures all workers terminate when reading
61                            STDIN for MCE releases 1.511 and below.
62
63                               cat big_input_file | ./mce_script.pl | head -10
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65                            This works fine without the -setpgrp option:
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67                               ./mce_script.pl < big_input_file | head -10
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69       Nothing is exported by default. Exportable are 1 variable and 2
70       subroutines.
71
72        use MCE::Signal qw( $tmp_dir stop_and_exit sys_cmd );
73        use MCE::Signal qw( :all );
74
75        $tmp_dir          - Path to the temporary directory.
76        stop_and_exit     - Described below
77        sys_cmd           - Described below
78
79   stop_and_exit ( [ $exit_status | $signal ] )
80       Stops execution, removes temp directory, and exits the entire
81       application.  Pass 'INT' to terminate a spawned or running MCE session.
82
83        MCE::Signal::stop_and_exit(1);
84        MCE::Signal::stop_and_exit('INT');
85
86   sys_cmd ( $command )
87       The system function in Perl ignores SIGINT and SIGQUIT. These 2 signals
88       are sent to the command being executed via system() but not back to the
89       underlying Perl script. For this reason, sys_cmd was added to
90       MCE::Signal.
91
92        ## Execute command and return the actual exit status. The perl script
93        ## is also signaled if command caught SIGINT or SIGQUIT.
94
95        use MCE::Signal qw(sys_cmd);   ## Include before MCE
96        use MCE;
97
98        my $exit_status = sys_cmd($command);
99

DEFER SIGNAL

101   defer ( $signal )
102       Returns immediately inside a signal handler if signaled during IPC.
103       The signal is deferred momentarily and re-signaled automatically upon
104       completing IPC. Currently, all IPC related methods in "MCE::Shared" and
105       one method "send2" in "MCE::Channel" set the flag $MCE::Signal::IPC
106       before initiating IPC.
107
108       Current API available since 1.863.
109
110        sub sig_handler {
111           return MCE::Signal::defer($_[0]) if $MCE::Signal::IPC;
112           ...
113        }
114
115       In a nutshell, "defer" helps safeguard IPC from stalling between
116       workers and the shared manager-process. The following is a
117       demonstration for Unix platforms. Deferring the signal inside the
118       "WINCH" handler prevents the app from eventually failing while resizing
119       the window.
120
121        use strict;
122        use warnings;
123
124        use MCE::Hobo;
125        use MCE::Shared;
126        use Time::HiRes 'sleep';
127
128        my $count = MCE::Shared->scalar(0);
129        my $winch = MCE::Shared->scalar(0);
130        my $done  = MCE::Shared->scalar(0);
131
132        $SIG{WINCH} = sub {
133           # defer signal if signaled during IPC
134           return MCE::Signal::defer($_[0]) if $MCE::Signal::IPC;
135
136           # mask signal handler
137           local $SIG{$_[0]} = 'IGNORE';
138
139           printf "inside winch handler %d\n", $winch->incr;
140        };
141
142        $SIG{INT} = sub {
143           # defer signal if signaled during IPC
144           return MCE::Signal::defer($_[0]) if $MCE::Signal::IPC;
145
146           # set flag for workers to leave loop
147           $done->set(1);
148        };
149
150        sub task {
151           while ( ! $done->get ) {
152              $count->incr;
153              sleep 0.03;
154           };
155        }
156
157        print "Resize the terminal window continuously.\n";
158        print "Press Ctrl-C to stop.\n";
159
160        MCE::Hobo->create('task') for 1..8;
161        sleep 0.015 until $done->get;
162        MCE::Hobo->wait_all;
163
164        printf "\ncount incremented %d times\n\n", $count->get;
165

INDEX

167       MCE, MCE::Core
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AUTHOR

170       Mario E. Roy, <marioeroy AT gmail DOT com>
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174perl v5.30.1                      2020-02-09                    MCE::Signal(3)
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