The theory is described here, but in my experience this doesn't work as advertised...

For example, this is what I get on the Linux box (SuSE 10.2) I'm sending this from: 

#!/usr/local/perl/5.10.0/bin/perl

use strict;
use warnings;

use POSIX;
use Data::Dumper;
$Data::Dumper::Useqq = 1;

my $inf;
my $sender_pid;

POSIX::sigaction(
           SIGINT,
           POSIX::SigAction->new(
               sub {
                   $inf = Dumper \@_;
                   $sender_pid = unpack "x16S", $_[2];     # <--
               },
               0,
               POSIX::SA_SIGINFO
           ),
       );

kill 'INT', $$;

print $inf;
print "Sender PID: $sender_pid\n";
print "Own PID:    $$\n";

__END__
$VAR1 = [
          "INT",
          {
            "code" => 0,
            "signo" => 2
          },
          "\2\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0RQ\0\0005\4\0\0\270\273}\0\
+0\0\0\0`\257i\0\0\0\0\0\3342E\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0
+\0\370\25e\0\0\0\0\0\30 e\0\0\0\0\0\1\0\0\0\0\0\0\0\r\0\0\0\0\0\0\0\3
+60b8\213\377\177\0\0\370b8\213\377\177\0\0\1\0\0\0\0\0\0\0\3IM\0\0\0\
+0\0"
        ];
Sender PID: 20818   (as we're sending the signal ourself, the sender i
+s $$)
Own PID:    20818

[download]

Ideally - as I'm reading the docs - there should also be hash fields for 'pid' (the process id generating the signal), 'uid', etc. — not available in this case, though.

With a bit of luck (and reading through your system's siginfo.h — (e.g. /usr/include/asm-generic/siginfo.h on my system)), you might be able to extract the relevant info from the raw siginfo struct dump...

Update:  unpack "x16S", ... looks promising — at least in my case, it extracts the appropriate PID  (see $sender_pid in the above updated snippet).  But be sure to test its portability, before you make this a vital part of your application...! :)

In reply to Re: Signal Handler by almut
in thread Signal Handler by lakshmananindia

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