A weird problem while executing nmap and fetching its output

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

Hello, I'm running into a strange problem when trying to execute nmap from Perl and fetching its output. The code looks like this:

my $cmd = "/usr/bin/nmap " . $self->settings . " -oX " . $self->report
+file . " -v " . $self->target . " |";
close STDOUT;
open(F, $cmd);

my $buf = "";
  while(<F>){
    $buf .= $_;
    #do something here
 }
[download]

It works well if the settings attribute is "-sT", but not if it is "-sU". So obivously i thought that it's a nmap problem, but if I print out $cmd and execute it manually it works like a charm.

So my question is, could this be in any way a Perl problem?

Comment on A weird problem while executing nmap and fetching its output Download Code

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Re: A weird problem while executing nmap and fetching its output by Anonymous Monk on Apr 11, 2013 at 01:54 UTC
It works well if the settings attribute is "-sT", but not if it is "-sU". What does that mean? -sU says it can be slow So my question is, could this be in any way a Perl problem? No	[reply]
Re^2: A weird problem while executing nmap and fetching its output by tobbo (Novice) on Apr 11, 2013 at 13:13 UTC
Thanks for your reply! Well yes, -sU is slow, but on startup nmap prints a version info. Also, to be a bit more perl related, shouldn't `while(<F>)` read until an EOF? So I suspect that the command doesn't execute at all, even though it is syntactically correct (if I print out the command and paste it to the commandline, everything works perfectly). Is the whole open a command as a filehandle syntactic sugar for fork/pipe/execute so i can debug from there?	[reply] [d/l]
Re^3: A weird problem while executing nmap and fetching its output by LanX (Saint) on Apr 11, 2013 at 13:27 UTC
> Is the whole open a command as a filehandle syntactic sugar for forkpipeexecute so i can debug from there? Well, like documented in open Cheers Rolf ( addicted to the Perl Programming Language)	[reply]