Simple(3) User Contributed Perl Documentation Simple(3)NAMEProc::Simple-- launch and control background processes
SYNOPSIS
use Proc::Simple;
$myproc = Proc::Simple->new(); # Create a new process object
$myproc->start("shell-command-line"); # Launch an external program
$myproc->start("command", # Launch an external program
"param", ...); # with parameters
$myproc->start(sub { ... }); # Launch a perl subroutine
$myproc->start(\&subroutine); # Launch a perl subroutine
$myproc->start(\&subroutine, # Launch a perl subroutine
$param, ...); # with parameters
$running = $myproc->poll(); # Poll Running Process
$exit_status = $myproc->wait(); # Wait until process is done
$proc->kill_on_destroy(1); # Set kill on destroy
$proc->signal_on_destroy("KILL"); # Specify signal to be sent
# on destroy
$myproc->kill(); # Kill Process (SIGTERM)
$myproc->kill("SIGUSR1"); # Send specified signal
$myproc->exit_status(); # Return exit status of process
Proc::Simple::debug($level); # Turn debug on
DESCRIPTION
The Proc::Simple package provides objects mimicing real-life processes
from a user's point of view. A new process object is created by
$myproc = Proc::Simple->new();
Either external programs or perl subroutines can be launched and
controlled as processes in the background.
A 10-second sleep process, for example, can be launched as an external
program as in
$myproc->start("/bin/sleep 10"); # or
$myproc->start("/bin/sleep", "10");
or as a perl subroutine, as in
sub mysleep { sleep(shift); } # Define mysleep()
$myproc->start(\&mysleep, 10); # Launch it.
or even as
$myproc->start(sub { sleep(10); });
The start Method returns immediately after starting the specified
process in background, i.e. there's no blocking. It returns 1 if the
process has been launched sucessfully and 0 if not.
The poll method checks if the process is still running
$running = $myproc->poll();
and returns 1 if it is, 0 if it's not. Finally,
$myproc->kill();
terminates the process by sending it the SIGTERM signal. As an option,
another signal can be specified.
$myproc->kill("SIGUSR1");
sends the SIGUSR1 signal to the running process. kill returns 1 if it
succeeds in sending the signal, 0 if it doesn't.
The methods are discussed in more detail in the next section.
A destructor is provided so that a signal can be sent to the forked
processes automatically should the process object be destroyed or if
the process exits. By default this behaviour is turned off (see the
kill_on_destroy and signal_on_destroy methods).
METHODS
The following methods are available:
new (Constructor)
Create a new instance of this class by writing
$proc = new Proc::Simple;
or
$proc = Proc::Simple->new();
It takes no arguments.
start
Launches a new process. The "start()" method can be used to launch
both external programs (like "/bin/echo") or one of your self-
defined subroutines (like "foo()") in a new process.
Starting External Programs
For an external program to be started, call
$status = $proc->start("program-name");
If you want to pass a couple of parameters to the launched program,
there's two options: You can either pass them in one argument like in
$status = $proc->start("/bin/echo hello world");
or in several arguments like in
$status = $proc->start("/bin/echo", "hello", "world");
Just as in Perl's function "system()", there's a big difference between
the two methods: If you provide one argument containing a blank-
separated command line, your shell is going to process any meta-
characters (if you choose to use some) before the process is actually
launched:
$status = $proc->start("/bin/ls -l /etc/initt*");
will expand "/etc/initt*" to "/etc/inittab" before running the "ls"
command. If, on the other hand, you say
$status = $proc->start("/bin/ls", "-l", "*");
the "*" will stay unexpanded, meaning you'll look for a file with the
literal name "*" (which is unlikely to exist on your system unless you
deliberately create confusingly named files :). For more info on this,
look up "perldoc -f exec".
Starting Subroutines
If, on the other hand, you want to start a Perl subroutine in the
background, simply provide the function reference like
$status = $proc->start(\&your_function);
or supply an unnamed subroutine:
$status = $proc->start( sub { sleep(1) } );
You can also provide additional parameters to be passed to the
function:
$status = $proc->start(\&printme, "hello", "world");
The start Method returns immediately after starting the specified
process in background, i.e. non-blocking mode. It returns 1 if the
process has been launched sucessfully and 0 if not.
poll
The poll method checks if the process is still running
$running = $myproc->poll();
and returns 1 if it is, 0 if it's not.
kill
The kill() method:
$myproc->kill();
terminates the process by sending it the SIGTERM signal. As an
option, another signal can be specified.
$myproc->kill("SIGUSR1");
sends the SIGUSR1 signal to the running process. kill returns 1 if
it succeeds in sending the signal, 0 if it doesn't.
kill_on_destroy
Set a flag to determine whether the process attached to this object
should be killed when the object is destroyed. By default, this
flag is set to false. The current value is returned.
$current = $proc->kill_on_destroy;
$proc->kill_on_destroy(1); # Set flag to true
$proc->kill_on_destroy(0); # Set flag to false
signal_on_destroy
Method to set the signal that will be sent to the process when the
object is destroyed (Assuming kill_on_destroy is true). Returns the
current setting.
$current = $proc->signal_on_destroy;
$proc->signal_on_destroy("KILL");
redirect_output
This allows to redirect the stdout and/or stderr output to a file.
Specify undef to leave th
# stdout to a file, left stderr unchanged
$proc->redirect_output ("/tmp/someapp.stdout", undef);
# stderr to a file, left stdout unchanged
$proc->redirect_output (undef, "/tmp/someapp.stderr");
# stdout and stderr to a separate file
$proc->redirect_output ("/tmp/someapp.stdout", "/tmp/someapp.stderr");
Call this method before running the start method.
pid Returns the pid of the forked process associated with this object
$pid = $proc->pid;
t0 Returns the start time() of the forked process associated with this
object
$t0 = $proc->t0();
t1 Returns the stop time() of the forked process associated with this
object
$t1 = $proc->t1();
DESTROY (Destructor)
Object destructor. This method is called when the object is
destroyed (eg with "undef" or on exiting perl). If kill_on_destroy
is true the process associated with the object is sent the
signal_on_destroy signal (SIGTERM if undefined).
exit_status
Returns the exit status of the process as the $! variable
indicates. If the process is still running, "undef" is returned.
wait
The wait method:
$exit_status = $myproc->wait();
waits until the process is done and returns its exit status.
debug
Switches debug messages on and off --Proc::Simple::debug(1)
switches them on, Proc::Simple::debug(0) keeps Proc::Simple quiet.
NOTE
Please keep in mind that there is no guarantee that the SIGTERM signal
really terminates a process. Processes can have signal handlers defined
that avoid the shutdown. If in doubt, whether a process still exists,
check it repeatedly with the poll routine after sending the signal.
REQUIREMENTS
I'd recommend using perl 5.6.0 although it might also run with 5.003 --
if you don't have it, this is the time to upgrade!
LEGALESE Copyright 1996 by Mike Schilli, all rights reserved. This
program is free software, you can redistribute it and/or modify it
under the same terms as Perl itself.
AUTHOR
Michael Schilli <michael@perlmeister.com>
Contributors:
Tim Jenness <t.jenness@jach.hawaii.edu>
did kill_on_destroy/signal_on_destroy/pid
Mark R. Southern <mark_southern@merck.com>
worked on EXIT_STATUS tracking
Tobias Jahn <tjahn@users.sourceforge.net>
added redirection to stdout/stderr
Clauss Strauch <Clauss_Strauch@aquila.fac.cs.cmu.edu> suggested the
multi-arg start()-methods.
Chip Capelik contributed a patch with the wait() method.
Jeff Holt provided a patch for time tracking with t0() and t1().
Brad Cavanagh fixed RT33440 (unreliable $?)
POD ERRORS
Hey! The above document had some coding errors, which are explained
below:
Around line 178:
You forgot a '=back' before '=head2'
Around line 282:
'=item' outside of any '=over'
Around line 720:
You forgot a '=back' before '=head1'
perl v5.14.0 2009-07-09 Simple(3)
