This time, too, the operations are quite lengthy, and I only have a personal laptop for these computations. In the evening I like to go home, but stopping a 2-hour computation and waste it is not good (some of you may recall I'm not new to this kind of problems: Variable persistence for suspend-and-resume programs). So, I implemented a save-and-resume mechanism inside the Java code, based on the test for presence of a file inside the filesystem as a signal from the outside to stop computing, save all and exit. Yes, I don't even want to know how Java handles real signaling.

In the Perl script, I set $SIG{INT} to generate the given file as follows:

$SIG{INT} = sub {
   open my $fh, ">PleaseStop" or warn "open(PleaseStop): $!";
}
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At the very start of the program I also wipe out the PleaseStop file, of course. Then, later in the program, I called the Java app like this:

my $outcome = qx/java MyClass param1 param2 param3 ... /;
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As you may guess, this approach fails half of the time to give the required graceous-stop behaviour. After some time, I realised that the backtick/qx operator actually calls fork() at some time, and I probably end up with two possible situations: in the desired one the Perl script is receiving the INT when I hit CTRL-C; in the other, it's the Java program that receives the signal.

As anticipated, I have no will to dig the secrets of signal handling in Java, so I worked out the following solution: disabling the INT signal before the call to the Java program, but not in the main Perl script:

# When it's time to call... call call_command
sub call_command {
   my $command = shift;
   my ($pid, $rd, $wt);
   {
      local $SIG{INT} = 'IGNORE';
      $pid = open2($rd, $wt, $command); # From IPC::Open2
   }
   my $outcome = join "", <$rd>;
   waitpid $pid, 0;
   return $outcome;
}
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Yes, I know that the call to waitpid should be more robust, but this is not a widespread script and I can live with it.

Is this approach correct, or should I do something better? Do you see troubles in my future with this? I work with Perl 5.8.6 in Linux (kernel 2.4), and I don't plan to use the script other than in this environment.