Exit codes and signals

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

Dear Monks, I have a process that forks into a parent that runs a monitor and a child that again runs another grandchild process. The grandchild process can terminate with 0 or non-zero exit code, which I can receive in the forked process, and return to the parent. But if the grandchild terminated due to a TERM signal, the exit code seen by the parent monitor is zero.

elsif ($pid == 0) {
# ....
my $exitstatus = ...
my $returnvalue = $exitstatus >> 8;
my $signalled = ($exitstatus & 127);
print "status=$exitstatus, signal=$signalled\n";
return($returnvalue);
}
[download]

In the above, I would like to return the full $exitstatus so the monitor can know the reason the grandchild quit. One possibility, although I am unsure how unconventional, is to return ($returnvalue | $signalled). Any help is greatly appreciated.

Comment on Exit codes and signals Download Code

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Re: Exit codes and signals by kennethk (Abbot) on Feb 06, 2016 at 15:14 UTC
Do you mean `exit $returnvalue;`, or am I missing something? exit #11929 First ask yourself `How would I do this without a computer?' Then have the computer do it the same way.	[reply] [d/l]
Re^2: Exit codes and signals by Anonymous Monk on Feb 06, 2016 at 18:48 UTC
yes, exit($returnvalue). The point being that I want to inform the monitor (gp) that the whole thing stopped early due to signal as opposed to normal termination indicate by exit(0).	[reply]
Re: Exit codes and signals by ikegami (Patriarch) on Feb 07, 2016 at 05:25 UTC
`bash` does `exit($? & 0x7F ? ($? & 0x7F) \| 0x80 : $? >> 8);` [download]	[reply] [d/l] [select]
Re: Exit codes and signals by Anonymous Monk on Feb 06, 2016 at 15:39 UTC
One possibility, although I am unsure how unconventional, is to return ($returnvalue \| $signalled). bash, for instance, returns 128+n if the command is terminated by signal n. It works well enough in practice... otoh, `$returnvalue \| $signalled` is probably less useful: `$ perl -mPOSIX -E 'say for POSIX::SIGHUP, POSIX::EXIT_FAILURE' 1 1` [download] Another possiblity is to use a more sophisticated form of IPC, some kind of message queue, perhaps (but that's maybe overkill in this case).	[reply] [d/l] [select]