Provided by: libproc-background-perl_1.10-1_all 
NAME
Proc::Background - Generic interface to Unix and Win32 background process management
SYNOPSIS
use Proc::Background;
timeout_system($seconds, $command, $arg1);
timeout_system($seconds, "$command $arg1");
my $proc1 = Proc::Background->new($command, $arg1, $arg2);
my $proc2 = Proc::Background->new("$command $arg1 1>&2");
$proc1->alive;
$proc1->die;
$proc1->wait;
my $time1 = $proc1->start_time;
my $time2 = $proc1->end_time;
# Add an option to kill the process with die when the variable is
# DETROYed.
my $opts = {'die_upon_destroy' => 1};
my $proc3 = Proc::Background->new($opts, $command, $arg1, $arg2);
$proc3 = undef;
DESCRIPTION
This is a generic interface for placing processes in the background on both Unix and Win32 platforms.
This module lets you start, kill, wait on, retrieve exit values, and see if background processes still
exist.
METHODS
new [options] command, [arg, [arg, ...]]
new [options] 'command [arg [arg ...]]'
This creates a new background process. As exec() or system() may be passed an array with a single
single string element containing a command to be passed to the shell or an array with more than one
element to be run without calling the shell, new has the same behavior.
In certain cases new will attempt to find command on the system and fail if it cannot be found.
For Win32 operating systems:
The Win32::Process module is always used to spawn background
processes on the Win32 platform. This module always takes a
single string argument containing the executable's name and
any option arguments. In addition, it requires that the
absolute path to the executable is also passed to it. If
only a single argument is passed to new, then it is split on
whitespace into an array and the first element of the split
array is used at the executable's name. If multiple
arguments are passed to new, then the first element is used
as the executable's name.
If the executable's name is an absolute path, then new
checks to see if the executable exists in the given location
or fails otherwise. If the executable's name is not
absolute, then the executable is searched for using the PATH
environmental variable. The input executable name is always
replaced with the absolute path determined by this process.
In addition, when searching for the executable, the
executable is searched for using the unchanged executable
name and if that is not found, then it is checked by
appending `.exe' to the name in case the name was passed
without the `.exe' suffix.
Finally, the argument array is placed back into a single
string and passed to Win32::Process::Create.
For non-Win32 operating systems, such as Unix:
If more than one argument is passed to new, then new
assumes that the command will not be passed through the
shell and the first argument is the executable's relative
or absolute path. If the first argument is an absolute
path, then it is checked to see if it exists and can be
run, otherwise new fails. If the path is not absolute,
then the PATH environmental variable is checked to see if
the executable can be found. If the executable cannot be
found, then new fails. These steps are taking to prevent
exec() from failing after an fork() without the caller of
new knowing that something failed.
The first argument to new options may be a reference to a hash which contains key/value pairs to
modify Proc::Background's behavior. Currently the only key understood by new is die_upon_destroy.
When this value is set to true, then when the Proc::Background object is being DESTROY'ed for any
reason (i.e. the variable goes out of scope) the process is killed via the die() method.
If anything fails, then new returns an empty list in a list context, an undefined value in a scalar
context, or nothing in a void context.
pid Returns the process ID of the created process. This value is saved even if the process has already
finished.
alive
Return 1 if the process is still active, 0 otherwise.
die Reliably try to kill the process. Returns 1 if the process no longer exists once die has completed,
0 otherwise. This will also return 1 if the process has already died. On Unix, the following
signals are sent to the process in one second intervals until the process dies: HUP, QUIT, INT, KILL.
wait
Wait for the process to exit. Return the exit status of the command as returned by wait() on the
system. To get the actual exit value, divide by 256 or right bit shift by 8, regardless of the
operating system being used. If the process never existed, then return an empty list in a list
context, an undefined value in a scalar context, or nothing in a void context. This function may be
called multiple times even after the process has exited and it will return the same exit status.
start_time
Return the value that the Perl function time() returned when the process was started.
end_time
Return the value that the Perl function time() returned when the exit status was obtained from the
process.
FUNCTIONS
timeout_system timeout, command, [arg, [arg...]]
timeout_system 'timeout command [arg [arg...]]'
Run a command for timeout seconds and if the process did not exit, then kill it. While the timeout
is implemented using sleep(), this function makes sure that the full timeout is reached before
killing the process. timeout_system does not wait for the complete timeout number of seconds before
checking if the process has exited. Rather, it sleeps repeatidly for 1 second and checks to see if
the process still exists.
In a scalar context, timeout_system returns the exit status from the process. In an array context,
timeout_system returns a two element array, where the first element is the exist status from the
process and the second is set to 1 if the process was killed by timeout_system or 0 if the process
exited by itself.
The exit status is the value returned from the wait() call. If the process was killed, then the
return value will include the killing of it. To get the actual exit value, divide by 256.
If something failed in the creation of the process, the subroutine returns an empty list in a list
context, an undefined value in a scalar context, or nothing in a void context.
IMPLEMENTATION
Proc::Background comes with two modules, Proc::Background::Unix and Proc::Background::Win32. Currently,
on Unix platforms Proc::Background uses the Proc::Background::Unix class and on Win32 platforms it uses
Proc::Background::Win32, which makes use of Win32::Process.
The Proc::Background assigns to @ISA either Proc::Background::Unix or Proc::Background::Win32, which does
the OS dependent work. The OS independent work is done in Proc::Background.
Proc::Background uses two variables to keep track of the process. $self->{_os_obj} contains the
operating system object to reference the process. On a Unix systems this is the process id (pid). On
Win32, it is an object returned from the Win32::Process class. When $self->{_os_obj} exists, then the
process is running. When the process dies, this is recorded by deleting $self->{_os_obj} and saving the
exit value $self->{_exit_value}.
Anytime alive is called, a waitpid() is called on the process and the return status, if any, is gathered
and saved for a call to wait. This module does not install a signal handler for SIGCHLD. If for some
reason, the user has installed a signal handler for SIGCHLD, then, then when this module calls waitpid(),
the failure will be noticed and taken as the exited child, but it won't be able to gather the exit
status. In this case, the exit status will be set to 0.
SEE ALSO
See also Proc::Background::Unix and Proc::Background::Win32.
AUTHOR
Blair Zajac <blair@orcaware.com>
COPYRIGHT
Copyright (C) 1998-2005 Blair Zajac. All rights reserved. This package is free software; you can
redistribute it and/or modify it under the same terms as Perl itself.
perl v5.10.0 2009-07-05 Proc::Background(3pm)