MCE::Signal(3) Temporary directory creation/cleanup and signal handling


This document describes MCE::Signal version 1.608


use MCE::Signal qw( [-keep_tmp_dir] [-use_dev_shm] );
use MCE; ## MCE loads MCE::Signal when not present.
## Include MCE::Signal first for options to take effect.


This package configures $SIG{HUP,INT,PIPE,QUIT,TERM,XCPU,XFSZ} 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.

The temp dir resides under $ENV{TEMP}/mce/ for native Perl on Microsoft Windows.

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 arguments 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_sigmsg        - Do not display a message when receiving a signal
 -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 | ./ | head -10
                     This works fine without the -setpgrp option:
                        ./ < big_input_file | head -10

Nothing is exported by default. Exportable are 1 variable and 2 subroutines.

 $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 'TERM' to terminate a spawned or running MCE state.


sys_cmd ( $command )

The system function in Perl ignores SIGNINT 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);


 ## Creates tmp_dir under $ENV{TEMP} if defined, otherwise /tmp
 use MCE::Signal;
 use MCE::Signal qw( :all );
 ## Attempt to create tmp_dir under /dev/shm if writable
 use MCE::Signal qw( -use_dev_shm );
 ## Keep tmp_dir after script terminates
 use MCE::Signal qw( -keep_tmp_dir );
 use MCE::Signal qw( -use_dev_shm -keep_tmp_dir );




Mario E. Roy, <marioeroy AT gmail DOT com>