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    Proc::Simple 1.24
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NAME
    Proc::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!

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().

