MCE::Signal(3) User Contributed Perl Documentation MCE::Signal(3)
NAME
MCE::Signal - Temporary directory creation/cleanup and signal handling
VERSION
This document describes MCE::Signal version 1.863
SYNOPSIS
## Creates tmp_dir under $ENV{TEMP} if defined, otherwise /tmp.
use MCE::Signal;
## Attempts to create tmp_dir under /dev/shm if writable.
use MCE::Signal qw( -use_dev_shm );
## Keeps tmp_dir after the script terminates.
use MCE::Signal qw( -keep_tmp_dir );
use MCE::Signal qw( -use_dev_shm -keep_tmp_dir );
## MCE loads MCE::Signal by default when not present.
## Therefore, load MCE::Signal first for options to take effect.
use MCE::Signal qw( -keep_tmp_dir -use_dev_shm );
use MCE;
DESCRIPTION
This package configures $SIG{ HUP, INT, PIPE, QUIT, and TERM } to point
to stop_and_exit and creates a temporary directory. The main process
and workers receiving said signals call stop_and_exit, which signals
all workers to terminate, removes the temporary directory unless
-keep_tmp_dir is specified, and terminates itself.
The location of the temp directory resides under $ENV{TEMP} if defined,
otherwise /dev/shm if writeable and -use_dev_shm is specified, or /tmp.
On Windows, the temp directory is made under $ENV{TEMP}/Perl-MCE/.
As of MCE 1.405, MCE::Signal no longer calls setpgrp by default. Pass
the -setpgrp option to MCE::Signal to call setpgrp.
## Running MCE through Daemon::Control requires setpgrp to be called
## for MCE releases 1.511 and below.
use MCE::Signal qw(-setpgrp); ## Not necessary for MCE 1.512 and above
use MCE;
The following are available options and their meanings.
-keep_tmp_dir - The temporary directory is not removed during exiting
A message is displayed with the location afterwards
-use_dev_shm - Create the temporary directory under /dev/shm
-no_kill9 - Do not kill -9 after receiving a signal to terminate
-setpgrp - Calls setpgrp to set the process group for the process
This option ensures all workers terminate when reading
STDIN for MCE releases 1.511 and below.
cat big_input_file | ./mce_script.pl | head -10
This works fine without the -setpgrp option:
./mce_script.pl < big_input_file | head -10
Nothing is exported by default. Exportable are 1 variable and 2
subroutines.
use MCE::Signal qw( $tmp_dir stop_and_exit sys_cmd );
use MCE::Signal qw( :all );
$tmp_dir - Path to the temporary directory.
stop_and_exit - Described below
sys_cmd - Described below
stop_and_exit ( [ $exit_status | $signal ] )
Stops execution, removes temp directory, and exits the entire
application. Pass 'INT' to terminate a spawned or running MCE session.
MCE::Signal::stop_and_exit(1);
MCE::Signal::stop_and_exit('INT');
sys_cmd ( $command )
The system function in Perl ignores SIGINT and SIGQUIT. These 2 signals
are sent to the command being executed via system() but not back to the
underlying Perl script. For this reason, sys_cmd was added to
MCE::Signal.
## Execute command and return the actual exit status. The perl script
## is also signaled if command caught SIGINT or SIGQUIT.
use MCE::Signal qw(sys_cmd); ## Include before MCE
use MCE;
my $exit_status = sys_cmd($command);
DEFER SIGNAL
defer ( $signal )
Returns immediately inside a signal handler if signaled during IPC.
The signal is deferred momentarily and re-signaled automatically upon
completing IPC. Currently, all IPC related methods in "MCE::Shared" and
one method "send2" in "MCE::Channel" set the flag $MCE::Signal::IPC
before initiating IPC.
Current API available since 1.863.
sub sig_handler {
return MCE::Signal::defer($_[0]) if $MCE::Signal::IPC;
...
}
In a nutshell, "defer" helps safeguard IPC from stalling between
workers and the shared manager-process. The following is a
demonstration for Unix platforms. Deferring the signal inside the
"WINCH" handler prevents the app from eventually failing while resizing
the window.
use strict;
use warnings;
use MCE::Hobo;
use MCE::Shared;
use Time::HiRes 'sleep';
my $count = MCE::Shared->scalar(0);
my $winch = MCE::Shared->scalar(0);
my $done = MCE::Shared->scalar(0);
$SIG{WINCH} = sub {
# defer signal if signaled during IPC
return MCE::Signal::defer($_[0]) if $MCE::Signal::IPC;
# mask signal handler
local $SIG{$_[0]} = 'IGNORE';
printf "inside winch handler %d\n", $winch->incr;
};
$SIG{INT} = sub {
# defer signal if signaled during IPC
return MCE::Signal::defer($_[0]) if $MCE::Signal::IPC;
# set flag for workers to leave loop
$done->set(1);
};
sub task {
while ( ! $done->get ) {
$count->incr;
sleep 0.03;
};
}
print "Resize the terminal window continuously.\n";
print "Press Ctrl-C to stop.\n";
MCE::Hobo->create('task') for 1..8;
sleep 0.015 until $done->get;
MCE::Hobo->wait_all;
printf "\ncount incremented %d times\n\n", $count->get;
INDEX
MCE(3), MCE::Core(3)
AUTHOR
Mario E. Roy, <marioeroyA ATA gmailA DOTA com>
perl v5.28.2 2019-11-24 MCE::Signal(3)
mce 1.863.0 - Generated Thu Nov 28 09:12:48 CST 2019