Why cant i save output of tasklist.exe in an array?

swissknife has asked for the wisdom of the Perl Monks concerning the following question:

Hello Monks,

To make a decision further in my program, i need to check if a process is running or not and for that i am trying following.


use strict;
use warnings;
use Data::Dumper;

my $BACKUPSTATE = "tasklist.exe";
my $state = "ovbbccb";

    open (DDDD, "$BACKUPSTATE |") || die "Failed: $!\n";
    my @cmdout;
    while ( <DDDD> )
    {
        @cmdout = $_; 
    }
    close (DDDD);

    
print "Output of command is =" . Dumper(@cmdout);
[download]

i am expecting the complete output of command tasklist.exe but the output is just last line

output: Output of command is =$VAR1 = 'tasklist.exe                  2
+716 RDP-Tcp#1
             3      5\'936 K
';
[download]

How can i get complete output in array so later i can use it to grep $state

Comment on Why cant i save output of tasklist.exe in an array? Select or Download Code

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Re: Why cant i save output of tasklist.exe in an array? by Corion (Patriarch) on Apr 10, 2014 at 10:30 UTC
In your loop, you are overwriting all previously stored values: `@cmdout = $_;` [download] Maybe you wanted to push? Or maybe you wanted to directly read the output of the command into the array? `my @cmdout = qx($BACKUPSTATE);` [download] See perlop for `qx()` (in "Quote-Like Operators").	[reply] [d/l] [select]
Re: Why cant i save output of tasklist.exe in an array? by Bloodnok (Vicar) on Apr 10, 2014 at 10:29 UTC
The problem is in `@cmdout = $_;` - where you continually initialize the array with the current line, methinx you actually meant to code `push @cmdout, $_;` A user level that continues to overstate my experience :-))	[reply] [d/l] [select]
Re: Why cant i save output of tasklist.exe in an array? by Preceptor (Deacon) on Apr 10, 2014 at 16:27 UTC
As other monks mention - your problem is you overwrite the array `@cmdout = <DDDD>;` [download] Will probably do what you want. On a more general style point - I would suggest strongly that you use 3 argument open, instead of two arg, because interpolated variables are a good way to introduce bugs. `open ( my $dddd_fh, "\|-", $BACKUPSTATE ); my @cmdout = <$dddd_fh>; chomp(@cmdout); print Dumper(@cmdout);` [download]	[reply] [d/l] [select]
Re: Why cant i save output of tasklist.exe in an array? by kcott (Archbishop) on Apr 11, 2014 at 00:44 UTC
G'day swissknife, I see you got a couple of quick replies to your immediate problem. For future reference, check this from open: "If the `open` involved a pipe, the return value happens to be the pid of the subprocess." And this from kill: "If SIGNAL is either the number 0 or ... This is useful to check that a child process is still alive ..." [Read the full details, caveats, portability issues and so on for both of those.] As a general technique for checking on this sort of process, you can do something along these lines: `my $pid = open my $pipe, '-\|', ... ... if (kill 0 => $pid) { # actions if process alive } else { # actions if process not alive }` [download] -- Ken	[reply] [d/l] [select]
Re: Why cant i save output of tasklist.exe in an array? by Laurent_R (Canon) on Apr 10, 2014 at 17:51 UTC
You could probably make it even simpler with back ticks: my @cmdout = `tasklist.exe`; [download]	[reply] [d/l]