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system command to run a application

hem
User

Mar 25, 2010, 8:39 PM

Post #1 of 14 (695 views)

system command to run a application	Can't Post

Hi

I am trying to run a application (.exe) from a perl script and i using the system command to to it.It opens the application but the problem is that the scripts just sits there waiting on something.I tried using exec but it does not continues on to the next line and exits the script.

Any ideas what "system" command is waiting on and why its just sitting there.
I am doing:
system($Command)
Thanks in advance

Nila
User

Mar 25, 2010, 9:09 PM

Post #2 of 14 (692 views)

Re: [hem] system command to run a application [In reply to]	Can't Post

Try to get the return value or error message from system command.
Read the perl document for exec and system functions. If system function fails only it will wait , otherwise it will not wait.

Try this,

Code

system($com)==0 or die "system $com failed: $?";

7stud
Enthusiast

Mar 25, 2010, 9:30 PM

Post #3 of 14 (689 views)

Re: [hem] system command to run a application [In reply to]	Can't Post

Quote

Any ideas what "system" command is waiting on and why its just sitting there.

Yes. system() waits for the other program to finish executing. When the other program finishes executing, system() returns the exit code of the other program. Typically, an exit code of 0 means success, and any other value means something went wrong.

Here is an example:

1perl.pl:

Code

use strict; 
use warnings; 
use 5.010; 
 
my $status = system '2perl.pl'; 
say $status;

2perl.pl:

Code

#!/usr/bin/env perl 
 
use strict; 
use warnings; 
use 5.010; 
 
sleep 5; 
exit 0;

output:

Code

$ perl 1perl.pl   
(hangs for 5 seconds) 
0

(This post was edited by 7stud on Mar 25, 2010, 9:35 PM)

hem
User

Mar 25, 2010, 9:34 PM

Post #4 of 14 (686 views)

Re: [7stud] system command to run a application [In reply to]	Can't Post

so is it possible that the other program does not return anything . In that case will system just wait

7stud
Enthusiast

Mar 25, 2010, 9:37 PM

Post #5 of 14 (683 views)

Re: [hem] system command to run a application [In reply to]	Can't Post

Try running my example and commenting out the exit() call.

hem
User

Mar 26, 2010, 11:21 AM

Post #6 of 14 (669 views)

Re: [7stud] system command to run a application [In reply to]	Can't Post

i tried the script after commenting exit and it returned

But then i changed the system command to

use strict;
use warnings;

my $status = system 'notepad';
print " $status\n";

In this case the script hangs and waits until i kill notepad or ctrl C

Thanks

7stud
Enthusiast

Mar 26, 2010, 11:49 AM

Post #7 of 14 (668 views)

Re: [hem] system command to run a application [In reply to]	Can't Post

Notepad doesn't finish running until you close Notepad. When Notepad first appears, that doesn't mean it is done running. You can still type text into a Notepad file, save it, edit it, etc., right? That's because Notepad is still running. Notepad is what's called a "gui program". Gui programs run in an infinite loop, so they won't stop running unless you take some action to kill them.

Both system() and exec() wait for the specified program to finish executing. It sounds like what you are looking for is fork(). See here:

http://www.onperl.net/Starting-A-Child-Process

(This post was edited by 7stud on Mar 26, 2010, 12:02 PM)

FishMonger
Veteran

Mar 26, 2010, 12:00 PM

Post #8 of 14 (659 views)

Re: [hem] system command to run a application [In reply to]	Can't Post

It's unclear as to what your ultimate goal is, but maybe this is what you're needing.

Win32::Process - Create and manipulate processes.
http://search.cpan.org/~jdb/Win32-Process-0.14/Process.pm

hem
User

Mar 26, 2010, 2:03 PM

Post #9 of 14 (650 views)

Re: [FishMonger] system command to run a application [In reply to]	Can't Post

ok i changed the code to
use warnings;
use strict;
use Win32::Process;
use Win32;

sub ErrorReport{
print Win32::FormatMessage( Win32::GetLastError() );
}
my $ProcessObj;
Win32::Process::Create($ProcessObj,
"C:\\NetMeter\\Myapp.exe",
"notepad temp.txt",
0,
NORMAL_PRIORITY_CLASS,
".")|| die ErrorReport();

sleep(5);

my $exitcode;
Win32::Process::KillProcess($pid, $exitcode);

Where do i get $pid from ?

Thanks

Code

7stud
Enthusiast

Mar 26, 2010, 3:54 PM

Post #10 of 14 (642 views)

Re: [hem] system command to run a application [In reply to]	Can't Post

I imagine it's returned by Create().

hem
User

Mar 26, 2010, 4:07 PM

Post #11 of 14 (640 views)

Re: [7stud] system command to run a application [In reply to]	Can't Post

Looked up Win32::Process::Create($obj,$appname,$cmdline,$iflags,$cflags,$curdir)

return is
Returns non-zero on success, 0 on failure.

FishMonger
Veteran

Mar 26, 2010, 6:13 PM

Post #12 of 14 (638 views)

Re: [hem] system command to run a application [In reply to]	Can't Post

Code

#!/usr/bin/perl 
 
use warnings; 
use strict; 
use Win32::Process; 
use Win32::Process::Info; 
 
my $pi = Win32::Process::Info->new; 
 
Win32::Process::Create(my $ProcessObj, 
                       'C:\winnt\system32\notepad.exe', 
                       "notepad temp.txt", 
                       0, 
                       NORMAL_PRIORITY_CLASS, 
                       ".") 
or die ErrorReport(); 
 
my @info = grep {$_->{Name} =~ m/notepad/} 
$pi->GetProcInfo(); 
my $pid = $info[-1]{'Handle'}; 
print $pid; 
 
sleep 5; 
my $exitcode = 0; 
Win32::Process::KillProcess($pid, $exitcode); 
 
sub ErrorReport{ 
    print Win32::FormatMessage( Win32::GetLastError() ); 
}

rovf
Veteran

Mar 27, 2010, 9:04 AM

Post #13 of 14 (629 views)

Re: [hem] system command to run a application [In reply to]	Can't Post

Don't really the answer for your question, but maybe helpful too:

I don't use Win32::Process for this, but a special feature of the system command (passing the magical integer '1' as first parameter), for instance:

$pid = system(1, $cmd);

This starts $cmd as separate process. To check whether the process has been ended, use

use POSIX qw( WNOHANG );
$program_finished=waitpid($pid, WNOHANG);

To kill the process, use

kill(-9,$pid)

or, if you are gentle, send first signal 15 to give the process the chance to save the file, and fire with -9 if the process decided to ignore you.

FishMonger
Veteran

Mar 27, 2010, 10:27 AM

Post #14 of 14 (626 views)

Re: [rovf] system command to run a application [In reply to]	Can't Post

In Reply To

Nice...I completely forgot about that.

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