I'd love to find out that this is pilot error (sorceror's apprentice error?), but I
fear not. It looks for all the world like, in certain circumstances, even if you
attempt explicitly to re-establish a signal handler that's been used, it won't work a
second time.
$ perl -v
This is perl, v5.6.1 built for VMS_AXP
Script:
-- snip --
use strict;
use constant NL => "\n";
my $pid = $ENV {'HOLD_PID'};
print "Process ID is '$pid'.\n\n";
open (my $writeme, "| SPAWN /NOLOG") or die "\nCouldn't fork: $!\n\n";
print "Open succeeded.\n\n";
print $writeme 'SET VERIFY', NL;
print $writeme 'SET NOON', NL;
print $writeme 'WRITE SYS$OUTPUT "Command 1."', NL;
synchronize ();
print 'FooBar!', NL;
print $writeme 'WRITE SYS$OUTPUT "Command 2."', NL;
synchronize ();
print $writeme 'WRITE SYS$OUTPUT "Command 3."', NL;
print $writeme 'LOGOUT', NL;
close ($writeme) or die "Close failed: $!\n\n";
print "\nClose done.\n\n";
sub synchronize {
eval {
local $SIG {ALRM} = sub {die;};
print $writeme "PERL -e \"print kill (ALRM, 0x$pid)\"\n";
sleep;
};
sleep 1; # to let the output from the inner Perl get printed before we go on.
} # end sub synchronize
-- snip --
Results:
Process ID is '2B217025'.
Open succeeded.
SET NOON
WRITE SYS$OUTPUT "Command 1."
Command 1.
PERL -e "print kill (ALRM, 0x2B217025)"
1
FooBar!
WRITE SYS$OUTPUT "Command 2."
Command 2.
PERL -e "print kill (ALRM, 0x2B217025)"
1
and then it hangs. You have to control-C out of the Perl program, and then manually
STOP the two sub-processes which it has created (one directly by Perl via the piped
open, and a second by the explicit SPAWN command in the first).
Any ideas?
Thanks. / Tom Edelson
