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MAN page from Fedora 28 perl-System-Command-1.118-5.fc28.noarch.rpm

System::Command::Reaper

Section: User Contributed Perl Documentation (3)
Updated: 2016-06-02
Index 

NAME

System::Command::Reaper - Reap processes started by System::Command 

SYNOPSIS

This class is used for internal purposes.Move along, nothing to see here. 

DESCRIPTION

The System::Command objects delegate the reaping of childprocesses to System::Command::Reaper objects. This allows a userto create a System::Command and discard it after having obtainedone or more references to its handles connected to the child process.

The typical use case looks like this:

    my $fh = System::Command->new( @cmd )->stdout();

The child process is reaped either through a direct call to "close()"or when the command object and all its handles have been destroyed,thus avoiding zombies (which would be reaped by the system at the endof the main program).

This is possible thanks to the following reference graph:

        System::Command         |   |   |  ^|         v   v   v  !|        in out err  !|        ^|  ^|  ^|  !|        !v  !v  !v  !v    System::Command::Reaper

Legend:
    | normal ref
    ! weak ref

The System::Command::Reaper object acts as a sentinel, that takescare of reaping the child process when the original System::Commandand its filehandles have been destroyed (or when System::Command"close()" method is being called). 

METHODS

System::Command::Reaper supports the following methods: 

new

    my $reaper = System::Command::Reaper->new( $cmd, \%extra );

Create a new System::Command::Reaper object attached to theSystem::Command object passed as a parameter.

An optional hash reference can be used to pass extra attributes to the object. 

close

    $reaper->close();

Close all the opened filehandles of the main System::Command object,reaps the child process, and updates the main object with the statusinformation of the child process.

"DESTROY" calls "close()" when the sentinel is being destroyed. 

is_terminated

    if ( $reaper->is_terminated ) {...}

Returns a true value if the underlying process was terminated.

If the process was indeed terminated, collects exit status, etc. 

Accessors

The attributes of a System::Command::Reaper object are also accessiblethrough a number of accessors.

The object returned by "new()" will have the following attributes defined(as copied from the System::Command object that created the reaper):

pid
The PID of the underlying command.
stdin
A filehandle opened in write mode to the child process' standard input.
stdout
A filehandle opened in read mode to the child process' standard output.
stderr
A filehandle opened in read mode to the child process' standard error output.

After the call to "close()" or after "is_terminated()" returns true,the following attributes will be defined:

exit
The exit status of the underlying command.
core
A boolean value indicating if the command dumped core.
signal
The signal, if any, that killed the command.
 

AUTHOR

Philippe Bruhat (BooK), "<book at cpan.org>" 

ACKNOWLEDGEMENTS

This scheme owes a lot to Vincent Pit who on #perlfr provided thegeneral idea (use a proxy to delay object destruction and child processreaping) with code examples, which I then adapted to my needs. 

COPYRIGHT

Copyright 2010-2016 Philippe Bruhat (BooK), all rights reserved. 

LICENSE

This program is free software; you can redistribute it and/or modify itunder the same terms as Perl itself.


 

Index

NAME
SYNOPSIS
DESCRIPTION
METHODS
new
close
is_terminated
Accessors
AUTHOR
ACKNOWLEDGEMENTS
COPYRIGHT
LICENSE

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