Can I run a piece of code like child process?

[Anonymous Monk]

HI,I want to run a piece of code (i.e A subroutine) in my script and the main code will not wait for his done.
The main code should go on and will not be care of whether the subroutine run correctly.
I don't want to use fork(),because child process occupy too many memory.Is there a way?
Thank you!

Originally posted as a Categorized Question.

[AgentM]

use Threads; perlthrtut

[tilly]

Use fork anyways. It is more efficient than you think.

See Threads vs Forking (Java vs Perl) and subsequent discussion (particularly the article that KM pointed out).

And don't use threads if you care about reliability, stability, and all that. Perl's threading does...interesting things.

[=sjs=]

The short answer is yes. But it really depends on what you're doing as to whether it makes sense to. #!/usr/local/bin/perl my $string = "print \"hello\\n\";"; if (fork() == 0) { system "perl -e '$string'"; }

[OzzyOsbourne]

I honestly have not checked the overhead on win32::process, and most people seem to be against it but I use:

use Win32::Process;
@servers=('server1','server2','server3');

sub ErrorReport{
    print Win32::FormatMessage( Win32::GetLastError() );
        }

foreach $server (@servers){
    Win32::Process::Create($ProcessObj,
                "c:\\perl\\bin\\perl.exe",
                "perl.exe c:\\script.pl -s$server",
                0,
                NORMAL_PRIORITY_CLASS,
                ".")|| die ErrorReport();

    #$ProcessObj->Suspend();
    #$ProcessObj->Resume();
    #$ProcessObj->Wait(INFINITE);
}

With the wait remmed out, the sub will not wait for the process.

[Eradicatore]

From what I've experienced and researched so far on win32 and NT is that its easiest maybe to use fork. From what I can tell, fork on win32 is like a hybrid between a true fork and a thread. It doesn't create a new seperate process as seen by the task manager, but it also does not have access to global variables in the parent like a thread should.

My example shows how to use fork together with Tk to get web pages but not interfere with the gui. The child just sits there waiting for urls to get. You will have to add proxy support if you're behind a firewall though.

Oh, also, you want to make sure you download the right version of perl that supports fork. You can get this from active state at here

#!/usr/local/bin/perl 

use POSIX;
use Tk;
use LWP::UserAgent;
use URI::URL;

pipe(FROM_P, TO_C) or die "pipe: $!";
select(((select(TO_C), $| = 1))[0]);

my $ua = LWP::UserAgent->new;

if (!($pid = fork))
{
   close(TO_C);

   while($line = <FROM_P>) {
      print "Child Pid $$ just read this: $line\n";
      chomp($line);
      $url = $line;
      $file = 'yahoo.txt';
      my $req = HTTP::Request->new(GET => $url);
      $req->header('Accept' => 'text/html');
      $res = $ua->request($req, $file);
   };
}
 

my $mw = MainWindow->new();
$button = $mw->Button(-text => "click here to download yahoo web page"
+, -activebackground => 'red',
                     -command => \&printit)->pack();

print "i'm the parent about to mainloop\n";

MainLoop;



sub printit {
   print TO_C "http:\/\/www\.yahoo\.com\n";
}

Justin Eltoft

"If at all god's gaze upon us falls, its with a mischievous grin, look at him" -- Dave Matthews

[harpreet]

Thanks a lot guys for helping me out...even I was looking out for a way to run a child process without the parent process having to wait....thanks for helping Harpreet